I would like to leave some feedback on the Plex app on my Oculus Go as there are some minor annoyances when using it:
1) The viewing angle is quite low. If you compare it to the Oculus built in 'Theater' (Gallery), where you sit up a little higher, the experience is much nicer (particularly when you expand the video to its largest setting). After opening both apps back to back, I found myself having to look up when using the plex app, when the video was at full size, and because of this and the way the goggles are made the edges of the video getting distorted (not as noticeable in the Gallery app)
2) The menu system while video is playing is difficult to use. When you resize your screen, most of the time the 'tv' screen moves around and you have to reposition it, the pause/play/slider bar is often times too low or behind the junk on the table, and using the trigger doesn't immediately pause the video when you select the 'tv'. This probably all has mostly to do with too much dependance on the touchpad and could probably use some tweaking.
3) Suggestion: This has mostly to do with the distance between your face and screen due to it being a VR headset, but often times the video comes across as extremely blocky for high resolution video. It'd be nice if plex switched into SD mode when the 'tv' got below a certain size or use 'HD' mode if the video quality is too high (I mean 4k content looked better when transcoded into HD mode for me).
The watch together feature hasn't been released yet, but can't wait to try that out!