IMO, the easier one are black back, Auriga (Threafin), Vagabond.
WIll start to feed on pellet quite quickly. And usually no issue with frozen mysis.
If water quality is good, e.g. Aged tank. Golden Butterfly is also quite an easy species.
I have successfully keep the above in my tank with several other species and some of them for more than 1 year now.
Do note some species can grow really big. Do note, like angels, butterflies carry a fair bit of parasites on them.
So better quarantine them properly before introducing them to the main tank.