Plex reads films from a folder. StreamBridge makes that folder a virtual disk and fills each file in from your debrid service as Plex asks for it, so nothing big is stored on your Mac.
You pick a film and it finds a stream
Looks like movie files, holds about 25 MB of each
Scans it like any library folder
TV, phone, browser
Video streams from your debrid account into the virtual disk as Plex reads it
In the virtual disk a film is as big as the real file, but only its first bit is on your Mac. When Plex reads further in, or jumps ahead, StreamBridge fetches that part from your debrid service.
If a link expires mid-film it gets a new one, and if a source slows down it switches to another copy of the same file.
About 25 MB of each title stays on your Mac so scans and starts are quick: roughly 6 GB for 240 4K films. What you watch is kept for a while too, up to a limit you set, oldest first. Settings shows how much it's using.

StreamBridge adds the virtual disk to Plex as a library folder. Plex sees ordinary movie files, so artwork, watch history and remote streaming all work as usual, even though the films aren't on your drive.
The part that serves the films runs on its own, so quitting, restarting or updating the app doesn't stop what's playing on the TV.
There's no Docker, no config file and nothing to install on your TV.