You can do that nonetheless. Just do all your customizations via embedded meta tags and sidecar poster graphics files. Most things can be done this way, with no need to make any edits in the Plex user interface.
See I want a definitive solution to naming singles in Plex - #3 by OttoKerner
plus https://support.plex.tv/articles/215916117-adding-local-lyrics/
That way, all your custom data are stored inside your media files, which you can backup already with a simple file copy operation.
