No serpaes with a gourami. Preferably not with an angel either. They are too nippy for that.
Your tank is fine for angels, but it does limit your tankmates a bit. If you wanted a pair of angels and a bnp, you don't have much room left. You could still fit in a school of about 6 tetras that are either shape shaped or else over 2 inches. You have be careful about tankmates for angels since angels like to eat smaller fish. They are more predatory than many people know.
If you just want one angel, you could have 2 schools of other fish.
Bnp have a huge bioload. Plecos are messy fish. So, I would only recommend 2 if you limit the other tankmates and are very diligent on your water changes.
Some other school options would be corys, lemon tetras, Pristella tetras, rummy nose tetras, bleeding heart tetras, leopard danios, zebra danios, cardinal tetras, black neons tetras, and kuhli loaches.
If you just get one angel, then there is the honey gourami, dwarf gourami, paradise fish, pearl gourami, and pencilfish.
Pitbull plecos are small and peaceful. They need friends, so a pair or a trio is recommended. There are also clown plecos whoch stay small.