This is likely because pms is keeping 50~10000000000 copies of the poster artwork and snapshots. You can’t do anything about it. Its just the way PLEX is.The devs thought it is a good idea to save hundreds of pictures in different languages just in case you decide to learn a new language. Plex has you covered!
It has nothing to do with you plexpass
I chose this topic over dozens of other ones cause it shows the issue on multiple operating systems. People report many different things and are having different results. Go figure.