I just scanned my old movie library that I have in separate folders with a naming convention that Plex recommends. I realize this feature is still in beta but about a third of the matches are incorrect. Also, I would hope you'd use ThemovieDB to scrape background images instead of making thumbnails. Or the option to chose either file thumbnail or background art. TMDB also has Youtube links to trailers that would be fun to have accessible on channels. A button to fix a bad match would be helpful. Looking forward to this being 100 percent! Thanks!
You can use the option to fix an incorrect match on the web admin.
Having years in your file names helps a lot.
Could you give a sample of your movie file names so we can take a look?