Sorry, I realize this is an old thread. I'm new to unraid, and enjoying the massive file structure conversion so far ... it is definitely worthwhile in the end
This statement about "missing the point" by having a docker use UNC paths makes sense from a logical standpoint. That being said, peek behind the curtain at Plex and you'll find an annoyance that could easily be sidestepped if only the docker would allow for UNC paths like other versions of Plex
The annoyance is how Plex "serves" when choosing transcode/stream/play. If you have a client requesting a media file from the docker, and the docker has (at the endpoint after translation) assigned that path to something along the lines of /mnt/disk/movies/etc(year)/etc(year).ext --> then your playback app (Plex) is going to take a stroll out to the network and say "I can't access /mnt" so please stream this file to me, oh mighty plex docker. That results in the file being cut-up by the docker and served out across the network. If you have a beefy server with plenty of disk io for the container or do something clever with where the docker chooses to "cut-up" the movie then there is never any resource issue. Note this is essentially the same thing as transcoding, but the difference is there is much less CPU overhead since it is only choosing to break up the file as opposed to encoding it on the fly. If you lower down the "allowed" bitrate on the client it will do the same thing, but request your CPU to encode small bits of the source file then begin serving them to the client. Higher bitrates and "original quality" settings on the client will not get around this issue if the playback client cannot directly access the file it is playing. The only way around this is to have a library with UNC paths that the brainless plex "clients" can see
Also, FWIW, pointing your plex libraries to a large user share would be a very streamlined way to setup plex