Sounds like a beautiful fish and a nice setup to come!
I'm not really an expert on angels, so I can't answer. I have heard that a larger group will fare better than three as long as the tank is large enough and well planted to give them space, but I don't know if that's true or just some lore I heard around that time. I know some people keep groups of angels in some tanks, so I'm assuming there's some equation of space and numbers that is feasible. I just don't know what it is. Maybe someone else here with more experience can comment. And who knows....my pair may just have been particularly aggressive.
For what it's worth, I saw no signs of aggression whatsoever until the mating pair was ready to spawn, and then it was like Jekyll and Hyde. The change from peaceful tankmates of the third angel to relentless assassins was sudden and horrific.
Good luck, and post pictures if/when you can. It sounds like you are giving them a good home and preparing for any possible problems, so they are lucky fish
joy to the fishes in the deep blue sea
55, 30, 30, 20, 10, and 10-gal. freshwater tropical tanks