Unlikely that you will get two pairs. Maybe something that are really different.I currently have a pair of flame angels in my 150. I'd really like to add a couple flamebacks when I upgrade to my 250 in a few months. Any chance of two dwarf angel pairs coexisting in that size tank?
I had Coral Beauty spawn with Flameback in the past in a 420 gal tank. IMO if they interbreed, the male will kill each other. IMO there can’t be much different than these two species.