To MySQL or not to MySQL?

If your not using multiple devices I don’t think the effort, and probably reduction in library speed is worth it. If your letting the device that would be running the database sleep then I would strongly advise against it. Kodi gets very unhappy when the db becomes unavailable. Normally it will recover after a long delay but i’ve had it crash as well.

If you just want to make sure you don’t have to rebuild your library then you can setup a backup in the MyOSMC add-on.

As for dealing with paths you shouldn’t really need to manually edit for that. If you are doing an individual show then once you rename the file just update the library and then run a clean library to get rid of the duplicate. If your changing an entire source and don’t want to rescrape there is an alternative.