I think with most dwarf angels, the aggressiveness depends on luck (some are just more mellow than others), tank mates and size of tank. They are sometimes territorial.
I had one a while ago (Flame angel) that decided the middle area in the 120 g tank was his/hers. Any fish cruising through the area would grab its attention and get a quick chase. Nothing too bad though. More recently had an Eibli angel in a 75g that just did its own thing and left everyone alone. Both of those tanks had fish where, other than Chromis, the dwarf angel was the smallest.