Regarding Samsung TVs:
There is a difference between streaming media and playing it from a USB stick connected to the TV.
The problem, as mentioned in the linked post above (here), has to do with the streaming protocol used between the Plex Media Server and Samsung TVs.
When Plex direct plays media, it sends the entire file, including all audio and subtitle tracks, to the client.
Samsung TVs have a limit of 30 tracks in a stream, not a media file.
If there are over 30 tracks, Plex must direct stream (aka remux) to get below the 30 track limit.
There is another problem with subtitles, also referenced in the earlier post. When direct streaming, if subtitles are enabled, Plex will transcode the video to burn in the subtitles. Plex must do this to keep the video, audio, and subtitles in sync with each other.
None of the above applies when playing from a USB stick. The Samsung video app reads the media direct from the stick. None of the streaming protocols, the source of the limitations, are in use.
EDIT: There are also bandwidth limits imposed by Samsung. H.264/AVC has a limit of 60 Mbps. H.265/HEVC has a limit of 80 Mbps (4K TVs) or 100 Mbps (8K TVs). If the bandwidth limit is exceeded, Plex Media Server will transcode the video.
The bandwidth limitations are mentioned on the Samsung Developer site: Video Specifications
