I have not had experience with dwarf gouramis, although im quite interested in them. Blue gouramis are absolute bullies, so dont buy them, but dwarf gouramis... Not quite sure. Have heard from 1 pearson that they would be fine to go with fighter fish, so if they can go with fighter fish i guess they can go with anything. Hope this helps
I have a Blue and Gold gourami in the same tank and they get on great, best friends in fact.
There are always good and bad examples of mixing community fish but I agree that three spot gourami's in general haven't got the best rapor in the group. I would stay away from these anyway because they would require a larger tank.
Be careful with Dwarf gourami's as they aren't the most hardy fish around. I had some and they died for no reason