@DarkestKnight started doing this here:
72 Challenge Redux: Angels AND Demons
There were also a few threads about this I recall crawling across my homepage, you should be able to find them in the search.
My personal opinion, I think it’s not “angels” vs. “demons” but I’m sure there are some entities across all planes that don’t like each other. But from my readings no one refuses to work with you because you work with another. (Though I don’t read a lot of these posts.)
Nah, you should be able to do both. Unless you work with group 1 to do one thing and then work with group 2 to undo what you’re doing with group 1.