Settings - ‘Show Advanced’ - Plex for Windows - Player
Set “Video Playback Quality” to a lower setting. The higher settings apply very taxing additional filters, (“additional” as in having nothing to do with the basic playback). When they are combined with 4K resolution material, they can indeed produce considerable GPU load.
See HTPC Tips and Tricks - #4 by gbooker02 for a few more details about this.
(these filters are shared with Plex HTPC, as both apps use mpv as their player engine)
