I only played the game once. I side with the mages before and tried to keep all companions happy. By the end of the game I only really liked two of them. So I wanted to try something different.
What happens if you:
Kill the mages
Rival Anders
Rival Fenris
Don't recuit Isabella
I also want a snarky Hawke doing this. Is it possible and what happens?
You can do all of this. But while you can rival Anders and Fenris together, I don't think it works out that well. Anders is angry with you for being friendly with Templars, but Fenris seems to think you're the opposite.
Isabela's quest will play out the same, but it'll be a mystery who took the Tome of Koslun. It's not as dramatic. And Aveline just isn't funny without her, in general.
Meredith still goes crazy if you side with the Templars.. The artifact messed her up, but she also thinks you're just playing her.