Everything I do is manual, I don't really have duplicates unless I get singles then get the album once it releases. Even then, unless the single comes with extra bonus tracks (seems to be a lost past time, never see this anymore) I will delete the singles after.

Here is the forum post I originally found years ago to setup music picard to tag multiple genres, which is the only setup that I have that took extra effort and not just use out of the box defaults.

https://getmusicbee.com/forum/index.php?topic=35975.0

You don't need to get too complicated with scripts if you let Picard do all the tagging and renaming. In my experience it works pretty well with the default out of the box configuration. Just don't try to do your whole library at once, just go album by album and check each one is matching with the correct release. I was in the same boat about a decade ago and did the same, just a few albums a day getting tagged and renamed into a fresh music directory. And of course, make a backup first, just in case.

Lately I've been going through this process again because I messed up configuring Lidarr and many files got improperly renamed. Since they were all still properly tagged, fixing them has been easy, especially with Picard. I haven't really bothered to find all the stray files yet (they're still roughly in the right location) because Plex ignores the paths and just reads the tags so the misnamed files aren't even noticable in Plex