Plex is currently hosting movies, series, music, audiobooks, and podcasts. However, I'm working on moving the the audiobooks and podcasts over to Audio Bookshelf.
If there is a Movie or Series you want on plex that isn't currently available you can request it through Overseer. Keep in mind that this interface is new and has bugs. If would like to request something that is marked as available, but you can't find it on plex click the yellow report an issue button and say you can't find it on plex. If something you want to watch is marked as requested that means someone else has already requested it and you don't need to request it again.
I have yet to find a clean way to request new books/podcasts; Until I do please continue adding those request to the Google Keep list.
The free user is all you need. You do NOT need a "Plex Pass" or "Remote Watch Pass" the server has a plex pass linked to it, so you don't need to purchase one to have access to premium features.