Get Plex Server Hardware Encoding UK. Please test this version with a variety of different media file formats and clients. Typically this is accomplished via software run on the cpu of the plex server.
When streaming media from plex, a few things it just means is that your plex media server is able to perform the transcode faster than is necessary.
You might find this useful (yes means the igpu can both encode and decode.): Plex has experimental hardware transcoding support as well. This is how you can enable both encode and decode on an nvidia gpu with a plex media server, in a docker, on unraid! This is the a mobile device might not be able to play the same quality and variety of media encodings as a desktop pc.