As for filtering / identifying unmatched movies…
Once a file is scanned and known to Plex, a simple re-name should not throw it off balance. Instead Plex should be able to recognize this is a “known” file when you scan the library the next time based on a hash/fingerprint it stores in its database.
This is one of the reasons why you have to go through the “Plex Dance” to make Plex forget a record 
