You should only invite users to your PLEX Home that you really trust, since the only thing hindering those from becoming an admin over your PLEX server is a short 4-digit PIN.
movies/series libraries will most likely be accessible by all PLEX Home users. You can create music/photos/videos libraries for each user and asssign them their own or create libraries for all PLEX Home users.
There is a lot to cover but basically you only have to create one PLEX account that has a PLEX Pass to use all features and create Plex Home users to control the access to your media.
It is recommended to get PLEX Pass for your PLEX account because you can use hardware transcoding and any PLEX App on any platform for free if you have PLEX Pass, you need to manually enable hardware transcoding in the settings.).
All your media is mounted read only so that PLEX is not able to write to or change anything on your drives.