Plex Home Theater seems to work fine for the most part for me. I upgraded to High Sierra the day it was released (I think September 25?) and the only issue is that videos will freeze randomly for about 5-7 seconds, but the audio will keep playing, and then the video will speed up to catch up and then it will be back in sync. If I jump back 7 seconds or more, that will fix the issue too.
It's not consistent though. Sometimes it doesn't happen at all, sometimes it happens 2-3 times for one file. And it's not the file itself, because I can stream from the Plex app on an Apple TV just fine. Or across the network, I can open the file via VLC and it plays back just fine. Or I can open Plex on my iPhone and stream anything with no freezes. It is only when playing back via PHT that I have any freezing issues.
Plex Home Theater is running on a late-2014 Mac mini with 16GB of RAM and a 1TB Fusion Drive. Most recent version of macOS and PMS and PHT installed. All media is on a 5TB external USB 3 drive connected directly to the Mac mini.
I would like to avoid going to PMP, since I think the interface is horrible. Browsing through hundreds of movies in PMP is so much more tedious than on PHT! And you can only have poster/folder/list view for ALL libraries. I want my movies library to be in "poster" view while my other libraries to be in folder view. PHT does it just fine, so why can't PMP?