A small check at https://ark.intel.com/content/www/de/de/ark/products/77486/intel-core-i34150-processor-3m-cache-3-50-ghz.html shows me, that the cpu supports quicksync. It means you can use hardware transcoding (if you have a Plex pass). Maybe the quality is not a nice as a more modern cpu but it will do just fine with 1080p videos. Should be a very ok Plex server - if you already own the hardware. I would not be buy this ancient machine to become my next Plex server.