I had a coral beauty in my old 180L tank and it was peaceful and left the corals alone. Bi-colour angels are stunning looking fish. They are a bit more territorial than the coral beauty and from what I have read, are more likely to nip at corals than the coral beauty. They also grow to about 6" according to liveaquaria.com, so you are probably better off sticking the with CB.
They will eat pretty much anything. A balanced flake/pellet food would be your best bet, although they may accept nori also.