Human Noble: Goody-two-shoes all the way. I don't remember any options in the starting dialogue to be a dick to your family and servants. In addition, the betrayal of your family by Howe sets you up in some ways to be the anti-Howe, to at least percieve yourself as everything he is not. A human noble would always choose Harrowmont over Behlen IMHO, as he would see too many paralells between the treachery against his own family and Behlen's. Howe's alliance with Loghain makes it highly unlikely a noble human would spare Loghain. I know for self-interested reasons a male might pick Anora, but nothing about your character suggests you're the kind of calculating social climber who would do that.
I agree human noble doesn't seem like the background that sets up being nasty or a dick. Your family treats elves well, they're much beloved by the people, your father is pretty open and lenient about what can be said, and there's no indication you'd have any influence to be an ass.
I don't know about choosing Harrowmont over Bhelen. Depends on your opinion of hereditary rights and such. Harrowmont seems like the more honorable candidate, but if you believe the throne should pass to the descendant of the King, then Bhelen is the de-facto choice. My noble would have sided with Bhelen, except she took the documents to the Shaperate and discovered she was being asked to blatantly lie in order to prop him up, which seemed like a little much. Even then she was somewhat reluctant to help Harrowmont, cause Harrowmont seemed like an opportunist trying to take the throne from the rightful heir.
You're also right about the alliance with Loghain, for the most part. But as others have noted, if you're more politically minded or aware of the larger picture, there's good reason to spare Loghain even if he was allied with Howe. My human noble didn't - the knowledge that Loghain knew what Howe did to her family and rewarded him nevertheless was too much, but after seeing how he accepted it and everything, she felt bad about having him executed (and in fact, couldn't do it herself, Alistair had to step in and do it for her).
Mage: To my mind, mage RPing splits based upon your decision with Jowen. If you help Jowen, it shows you're "good," along with a naive fool to think you could break into the basement and kill a lot of things without anyone noticing. You become a cliched stupid good white knighter. Turning him in to the First Enchanter shows you're more concerned about your own position in the Circle than helping your best friend - ironically, this sets you up much better to be "evil." However, any mage which chooses this path will have a lot of resentment towards the Templars (as you're exlied on their request over the First Enchanter's wishes), so you have no reason to be resentful towards the Circle, and there's no way in hell you'd side with them over the Templars. On the other hand, you're set up quite well to become a blood mage with this build.
This, as others have noted, depends strongly on how you feel about Jowan. If you accept that your friendship is strong, sure. But Jowan does indeed come off as the clingy, annoying friend that you might tolerate only because you don't want to tell him to get lost. Either way, Jowan's plan
really sucks. Even if you fully wanted to help him, they present no options for escape or covering up the crime, so that you wouldn't be blamed. You're asked to get a rod of fire to melt some locks - an action that leaves a damn paper trail to follow right to you. No matter how good you might be, unless you're a ****** you have to see there's going to be consequences for you, probably really serious ones like death or tranquility yourself. And since your phylactery is gone, you can't escape with him - not that he has an actual escape plan anyway (I suppose if the templars and Irving hadn't shown up he would have gone to the front door and asked them nicely to open it? Yeah...)
On the other hand, going to the First Enchanter does seem like a reasonable option, because you're shown him to be caring and "fatherly" up to that point. My first mage character, before I knew the options, went straight to Irving - not to turn Jowan in, but to get his help, figuring he might have a way to make everything allright. Of course at that point you kind of get roped into it one way or another, so you don't have the option to bow out after that.
City Elf: I know a lot of people choose this as their "evil" PC, but honestly, I just don't see it, at least from my runthrough as a male (I know female plays differently, I'll try it soon). While you should have a lot of resentment towards humans, particularly humans in power, and choose the dickish responses, your whole introductory story as a male is about heroism - risking your life for your kith and kin. Of course, you could take the buyout Vaughn offers you (probably the most evil act in the game). I could see how the female plays differently, as you're just out for survival and retribution.
Vaughan's buyout actually makes the most sense from a logical perspective, except for the fact that you can be pretty sure he wouldn't actually keep his word, and probably hurt the Alienage anyway. This one definitely does set you up to be evil to humans in my opinion, though. From the guards to the nobles, none of them seem to think much of elves and all of them are well aware of Vaughan's activities and don't seem to mind.
Dalish Elf: This sets you up to be a doll-eyed vulcan with no personality to speak of. I can't say enough bad things about it and the Dalish in general, who seem to have no personalities (besides Zathrian of course).
Not sure I agree with this, but I will say that the game isn't "different" enough overall for this viewpoint to feel right throughout the game. Most of the dialogue options you get are the same, and your Dalish origin doesn't seem to factor in all that much throughout the whole of the game, especially since it feels like you as a main character aren't treated as badly as elves, especially Dalish elves, "should" be throughout the game.
Noble Dwarf: The main themes of the origin are you were loved by the people, and you were betrayed by Behlen. You can be a total dick to commoners if you like, which helps in setting up a darker character, but the origin builds you up as a "hero." Regardless of how you play the character, you're the only origin with a really compelling reason to preserve the Anvil beyond getting some golem cannon fodder. You also ultimately want to pick Harrowmont, just to make sure your brother cannot ever profit off his betrayal.
The origin builds you up as the most popular of the King's sons, but says nothing about your morality, so you can be a backstabbing dwarf or a noble one. Either way you can be quite popular through the Provings or through putting on a good face and being personable, as it claims you are, compared to Trian.
As for the Anvil, I disagree entirely. In fact, the only origin I see as having a compelling reason to destroy the anvil is the casteless dwarf, who knows the souls to power the golems will probably come from casteless. Everyone else unless they're playing goodie-two-shoes and completely ignoring the Grey Warden philosophy will realize that the Anvil will help not only in this Blight, but could turn the tides in the deep roads, allowing the dwarves to eventually begin retaking their kingdoms and putting the world on the path to exterminating the darkspawn once and for all. The entire concept of the Wardens is that the ends justify the means, and sacrifices are necessary. No end could be more important than the possibility of eventually defeating the darkspawn entirely, and sacrificing people to turn them into golems seems a hell of a lot more efficient than sacrificing them to turn them into Grey Wardens. Golem success rate is implied to be 100% not low chance of surviving, and a golem is worth a dozen normal soldiers. Furthermore, if you think about it logically, it makes for an awesome alliance with the Wardens. When a Warden gets old enough that they would normally wander into the Deep Roads to die, they could instead become a golem, to continue fighting the darkspawn.
And then there's Bhelen and Harrowmont. Originally I agreed with your viewpoint that your only reasonable choice is Harrowmont, but that depends on whether you put yourself or your House first. A dwarf that puts his house first has no choice but to support Bhelen, because House Aeducan as a whole benefits if the Aeducans stay in power. A dwarf that sees his personal betrayal as paramount, however, would clearly side with Harrowmont simply for revenge on his brother.
Casteless Dwarf: I began this origin thinking I'd play it as an "evil" runthrough, but upon meeting my family, I found going that far didn't quite make sense. I actually agonized in conversation with the man I was sent to kill whether or not I would do it, although I finally reluctantly attacked him (mainly because my PC was worried about retribution if his boss ever found out he didn't do the deed). You're also the only character who's really moving on up in the world becoming a Grey Warden - besides your sister, you aren't really leaving anything behind of note, so you're probably the most stoked out of all the origins for your new position. When I get around to playing this PC through, I think I'll go the "practical" route. Willing to do good deeds - provided there's a monetary reward, and you don't get too put out by doing them. Also willing to do bad things, but not for the sake of being evil, just because they're the best of all possible choices. Clearly you choose Behlen in Orzammar. You probably turn down the Anvil though, as your realize your own folk will be the most likely to be made into golems.
Not sure I agree on the "evil" or not here. Castless is definitely a good start for the type that will do
anything to get ahead. After all, anything is worth it to get yourself and your family out of the rathole that is Dust Town. Having some people you care about doesn't eliminate the possibility of doing bad things to others, it simply means you're concerned about someone in addition to yourself. The practical route is the most reasonable for the dwarf commoner, I agree.
There's a few game decisions I just have a hard time seeing anyone make. Persuading the werewolves to kill all the Dalish, for example, only makes sense if you metagame and know you'll get a werewolf army. Since the PC doesn't have a treaty from the werewolves, they have no way of knowing that, and no origin sets you up to hate the elves enough. Siding with the cultists also doesn't really make sense to me with any origin story unless you metagame because you want to unlock Reaver.
Here, I agree for the most part. Persuading the werewolves to kill all the dalish sort of makes sense if you think you can force them to serve as a replacement for them in your army, though. You can think about it along the lines of taking a risk and hoping they will help you afterward, for the possibility of getting much stronger troops.
Siding with the cultists however makes no sense under any origin unless you're a moustache-twirling caricature of evil, just out to do evil things for evil's sake. A bunch of random mooks that live up a mountain, you killed the vast majority of them so they have nothing to aid you with, and they wouldn't aid you even if they had the resources to? Clearly, having possession of an artifact that can cure any disease or poison is better! If you're selfish, or against the Chantry, you kill Genitivi to make sure he doesn't tell anyone where it is, and presumably you go destroy his notes and all, to ensure the location of the urn is kept as secret as possible. Otherwise you share the location with the rest of the world and such, but destroying the ashes in return for...unspecified and highly vague "knowledge" that they promise you is hardly a reasonable option.