The first Jellyfin setting I enable gives me a feature that Plex puts behind a paywall

Transcoding is an unavoidable part of both the Plex and Jellyfin experiences. When it’s required, converting your videos in real time into a format that your client devices can handle is slow and resource-heavy and is the main cause of buffering and stuttering. But you can speed it up significantly by enabling hardware acceleration on both platforms. The big difference is that on Plex, you have to pay for it. On Jellyfin, it’s free.