I got to the point that Amethyst can now run two background video playbacks, one with Tor and one without Tor, at the same time.

That would happen when two videos are on the screen, one with a .onion address and another with a regular URL and Tor is disabled for video playback OR when two videos are on the screen and TOR is forced for videos, but one of them is coming from a server in the phone, which must use clearnet.

Background services are account agnostic, but listen to the currently active account to get the Tor settings from.

Edge cases, huge complexity, but this is the right way to do it.