I'm replaying the game now, so I'll be able to check that dialogue soon, but I think that Vivienne mentioned standing with the templars.
And given that the Circle is where elves of all people can reach any position that a human could--up to the point that an elf leads the entirety of the Circle--I find it incredibly unlikely that Vivienne being Rivaini would have barred her from advancement all that much. Especially since a mage Trevelyan can also be black.
I did some double checking and she does rally the Loyalist mages who take up arms against the rebellion, but I'm certain they did not fight on the side of the rebelling templars either. If we look at the rebellion it was more akin to a three-sided conflict with the Chantry, rebel mages, and templars. I did some research:
While the vote passed, it did so by a very slim margin. The other half of the mages who voted against secession were soon forced to fight the rebel mages, and united under First Enchanter Vivienne de Fer of the Montsimmard Circle. They identified themselves as "Loyalist" mages, wishing to reinstate the Circles and end the war. Meanwhile, the "Isolationist" mages, true to their name, chose to go into hiding rather than fight.
The implication here, which is held out by many of Vivienne's comments about the humanitarian cost of the rebellion (esp in the Hinterlands), is that they did not explicitly want to fight the other mages, the Loyalists simply sought an end to the conflict and a peaceful resolution (remember Viv proactively supports Cassandra's platform as Divine and her dialogue implies that she had the deepest respect for Justinia), but were forced into open conflict with the rebel mages because of their refusal to support the decision of the CoE (I can't find them off hand but I know there are codex entries about how some of the rebels turned on mages who had no wish to participate in the rebellion)
In 9:40 Dragon, in response to Justinia V's interference at the White Spire, Lord Seeker Lambert declared the Nevarran Accord, which had led to the Seekers and the Templars submitting to the Divine and establishing the Circle of Magi, to be null and void.
Cassandra: You would prefer to have the templars return to guarding the circles, Vivienne?
Vivienne: Of course, my dear. They need better oversight, clearly, but one does not throw away a tool because it was misused.
Cassandra: Few mages would ask for templars in the circle.
Vivienne: Speak to Ferelden's first enchanter. You might be surprised. When abominations ravaged your tower, suddenly the world holds far too few templars.
Vivienne as Divine:
To the surprise of many, she reinstates the Circle of Magi and creates a Templar Order firmly leashed to her hand.
Mages rise quickly in the new Circle, having more freedom and responsibility then ever before - even if all true power lies with her.
Using these as context clues, it would be extremely difficult to see Viv supporting the rebelling templars any more than she supports the rebelling mages. Viv isn't pro-templar she's pro-templar-usage and views them as a tool that is to be used for the benefit of mages and non-mages, not something that should go gallivanting off on its own making its own decisions. The fact that none of the Loyalist mages are ever seen/mentioned/implied to be chasing after the rebels in the Hinterlands/Redcliffe also helps support the idea that it wasn't a proactive fight against the rebel mages, at least not after the actions of the LS Lambert.
As to your second point - I don't think Viv ever cared to rise to power within the confines of the limited power mages hold in the Circles. I honestly think Viv wanted freedom as much as Anders, just not necessarily in the same context or through the same methods. She wanted genuine political power and the ability to have a real impact on the world/society around her (for better/worse Viv thought she was the lady for every job and all the jobs). She played the Game as a means through which she could free herself from the limitations of the Circles and, if we look at her Divine ending, she will use her power to recreate that possibility for all mages. Viv may want templars to be part of the Circle, but she (ironically) uses her templars almost the same way the Tevinter Imperium uses theirs - as a tool for the mages rather than a power over over them. I don't like her as Divine because I don't think a system should rely upon the force of character of one person alone (Viv may be doing a good job in the positive epilogue, but what happens when she dies? too much of her system depends on her micromanaging everything) and Cass (even Lel) offer more sustainable systems due to their focus on rebuilding institutions rather than simply changing the leadership.
This is also why Viv is very "meh" about mages like Anders who think the only way to change the system is for them to blow up Chantries - I admit, I think she is blinkered here because she never lived in any of the harsher Circles and while she has heard about them second hand and does say "protest against the abuses of the templars" that's not a replacement for first hand experience - but within the context of her experience, it is a little "oh come on are you really saying we couldn't have done this differently? I was doing this differently and then all of you went and ruined the whole sodding show." I don't agree that Viv's methods are the best ones - I think systemic change is sometimes necessary to varying extents (go Cass!) - but there's nothing inherently wrong with being a top-down reformist the way she is, it's a valid perspective and works in some contexts and doesn't work in others.
Also in terms of skin color, I think the game sort of ignores all of your choices outside of species/gender/class because you have protag!armor for everything else (it's like Cullen in DAII being oblivious to Hawke's staff), but we definitely have Viv facing discrimination for her skin color:
Cole: Voices inside. Marquis Alphonse.
Cole: "I do hope Duke Bastien puts out the lights before he touches her. But then, she must disappear in the dark."
/side note I miss book analysis so much rn because then I can just ctrl/f my ebooks to find quotes and lore rather than all this blighted wiki googling and youtube surfing for quotes