They'll work, but you're less likely to encounter issues running the same model card, also, consider using windows over linux if you're new to the game, particularly if you're going to mix and match cards as, (At least from my experience) windows is a bit more friendly when it comes to that kind of setup.
Personally, My rigs are all 280x's so I have limited experience setting it up how you've proposed, however, I can say the Asrock board is awesome