Is this only for music, or tv shows as well? I find myself shuffling shows a lot and it was nice in Plex to have a smart playlist and exclude shows that had been played in the last X days from the playlist.

Sauce?

I went through this a bit ago. The calibration of your pace is set during an outdoor run. Try and do one or two outdoor runs at the same pace as the treadmill and it should adjust.

You should only have to backup the Postgres database. But it won’t hurt to have a copy of your compose file as well.

This GitHub issue has the steps you should use. And answers all your other questions too.