I have had a lot of gourami, blue, gold, moonlight, pearl, flame, powder, opaline, kissing, ect ect. They are by far the most individually different fish I have dealt with. I have had a male opaline that was crazy nippy, and another male that got bullied to death. Same with another moonlight pair. Usually they are good community tank fish, but they usually become the alpha when they mature. I have only had 1 kill another fish, but I think it was because the other fish wasn't healthy enough to defend itself.
It's always a good idea to keep each species alone. I currently have 4 (gold, opaline, blue, moonlight) in the tank, they have coexisted for over 2 years. There is a clear pecking order being the moonlight then opaline then gold then blue. They are males from what I can tell. But it's not fighting, just warnings.
There is nothing wrong with a pecking order in the tank. If your three spot in the alpha, but not killing any other fish, and they can live happily, there's no problem. Usually they will just nipp a couple times and then call it quits. I haven't often seen constant, nonstop chasing they will kill a fish.