re: disconnecting them from other devices, etc...I had already tried that right from the beginning, and it's still not working. I did look for some sort of compatibility guide for headphones as well, but couldn't find anything. I'll keep looking though, just in case I missed it. And I can't find anything on either set of headphones to change a pairing mode at all, or even any evidence that there are different modes for them, but I'll keep checking on that front as well.
In terms of controlling the Mini with the google app, that unfortunately doesn't do what I'm looking for - unless I've missed a way to make that use bluetooth, but it only seems to be wifi. Ah well - guess maybe I'll have to do the annoying wifi/hotspot shuffle each time I change places when I travel; it's a bit irritating but I'd definitely rather not bring the large remote with me. (Although if I can't get any of my travel headphones to pair I may have to take some other device travelling anyway.) Thanks!