My thoughts on the Amazon puffers was that they are the only puffers not known for aggression, and their diet matches that of a potential eel (easier when they both eat the same thing). They do need groups too, if I could only get one it would make for a much lower bioload.
My main concerns with each is that for the puffers, I’m not the biggest fan of pufferfish, with wolves I would have been hoping for a community (though red wolves are freakin awesome), and scorpionfish are brackish which makes water chemistry exponentially harder to keep in check.