Royal grammas are so pretty. Just so you know, though, mine comes out in the morning and then just periodically during the day. He stays in the rocks a lot, not a really active swimmer. Of course, each individual fish is different, though. I have chalk bass in my 30g, he's out all the time, and the angel doesn't pick on him.
I think that as long as you're really good about doing PWC
and keeping water params in check, you could do 4-5 fish, but the rest would need to be small fish. Nothing as big as the angel. Firefish are great. Clown gobies are cute too.