I have formed pairs only.
Flame, Lemon Peel, Coral Beauty, Pygmy/Chrub and Keyhole angels.
All the Flames I've had tend to pick at corals and clams. Devistated a huge Lepto coral once. Killed 2 clams.
I always started with the smallest/youngest I could get and let them sort it out. Don't get fully adult angels as the 2 times I've done this the gender was evidently set and they either fought and one killed the other or one jumped out. Young angels are female. The most dominate/larger one usually will be the male.
Sorting out which ends up male or female usually takes a few months of chasing. I've done Flame, Coral Beauty and Lemon Peel in a 180 gallon display tank at the same time. In that case they ignored the conspecifics and focused on each other. Also in this one case the Flames ignored everything but the clams. Only 1 ate my two clams after they paired up.
Matt P. Formed a Pygmy/chrub harem with 3 but IIRC one was later killed.
Hope this helps