You do have to follow the naming scheme, though 95% of the time I don’t need to touch the names of tv show episodes, just stick them in the correct folders. The exceptions are mostly anime and shows I could only find on internet archive, as, for some reason, those often come with just the episode number in the name, not the full “s01e14” that basically everyone else uses.

I rename my movies but that takes maybe ten seconds per one I add, tops, and the result is easier to read when managing files later than leaving them as “www.torrenting.com The.Matix.ita.eng.1999[rarbg]” or whatever insane file names they usually come with.

But it also means I can't seed it, right?

I've been running a Plex/jellyfin server for years and never had to rename any files. Don't do that. Match them in Jellyfin and leave the original filenames intact.

If you rename them, you can re-create the whole library with auto scan, which is nice.

Do you mean you let it auto-scan the wrong id, go find that wrong movie in your library, then manually provide an e.g. IMDb id, for every one?