I have several push-in 9mm legged automotive power relays, 20-70A.
They have low current 12V control coils, but because they are in a plastic base, and because I've seen so many overheat and the components/contacts move, and because 12/2 mains cables look so much more robust than the contacts and contact arms look so wimpy, I'm not disposed to using them. There's also the issue of mounting and wiring them in an approved box.
Isn't there something available like this?
Re: 120v relay: there's something that scares me about the possibility of crossing 2 domestic circuits (of having the on/off 120v "signal" emanating from a 15A branch/preamp outlet controlling a 20A circuit's outlet. If they are of opposite phase, there would be 220v potential difference. phil