I’m a potato from Mandalore. This is the way.
You could create NFC cards with the cover of each movie and scan them to trigger the start of a movie on your collection.
I’ll open source when it’s ready to be taken apart by a bunch of judgy people. I also need to comment and add some Easter eggs.
You could try to use home assistant which has plugins for both plex and NFC. You may need to fool around with an ESP32 or arduino board to get it all working together.