Yoyos are great little fish. They are active and interesting, "pook" wonderfully, and have pretty patterns. As far as compatability, they go with just about anything that won't eat them, other than snails and shrimp. They like to escape, though, so make sure the tank is very secure. There would be no intake valves that are even CLOSE to loach-sized. And your tank should be completely covered, all the time (when not feeding or cleaning).
I have two, and while I feel a little sorry for the non-dominant one, I don't think that more are strictly necessary. I probably would get a third if I had a larger tank, though.
They make noise. Mine dig in the gravel, and try to jump out, both of which make lots of noise at night. They also can click, I think it is by forcing air out of their swimbladders through their ears? Mine haven't clicked since the first night, though.
Right now, the dominant one is sitting on a leaf of my plant, looking very cute.