Im confused. There are two different streaming things on Plex. They support streaming inside the plex app of content from the usual streaming services, much like Apple TV or your TV’s built in media manager. They also support streaming your collection across the internet to wherever you are. Which is now behind a paywall?
I don't use Plex anymore, but not long before I cancelled my account they starting charging to access someone's library that had been shared with you if the sharing party did not have Plex pass, or something to that effect.