Get an Intel 7th/8th/9th gen processor. Plex will use the on-board GPU for h/w accelerated transcoding. 7th gen & later support H265/4K/10-bit decode. 8th gen & later includes H265/4K/10-bit encode (Note that Plex currently transcodes 4K H.264/H.265 to H.264/8-bit/1080p max). Capabilities are listed in the data sheets for each generation. Look for the Processor Graphics section, usually in Datasheet, Volume 1 for each generation. 9th gen info included in 8th gen datasheet.
Alternately, look at a Nvidia P2000.
