Plex Home is a Plex Pass-feature. So anything I am describing below is only available with a Plex Pass.
A managed user uses still your Plex username and password to authenticate the Plex app. Only later he’ll be able to switch to his/her separate “area” where his ‘watched/unwatched’ is stored and the access restrictions to certain libraries etc come into effect.
What’s preventing a ‘managed’ user to going back to your ‘admin’ access level is just the 4-digit PIN number you set on your account.
Foe a person in a different household, I still recommend you to create a separate full user account on plex.tv. (it is free to create, you just need a separate email address)
You can later decide to add this separate plex.tv account into your Plex home.
While this will enable the free access to paid Plex apps (iOS, Android) it also activates
‘Fast User Switching’ which then presents again the potential security issue with the 4-digit PIN.
This is something you have to decide - if the person is trustworthy enough to not try 10000 times to find out your 4-digit PIN.
Without Plex Pass, your sharees need always a full plex.tv account (if you don’t want to share your plex account with them, which I don’t recommend)
and you can only decide per-library whether you share with the person or not.
https://support.plex.tv/hc/en-us/sections/200295083-Server-Sharing
