Plex has overhauled its apps from the ground up to make them easier to navigate. The teams says it will be able to roll out new features faster as well.
I think the transcode part is decided by the client, but in the Jellyfin server admin you can control if a client can request a transcode (which may not be actually needed - and if you know what client they are running it’s probably easier to decide). This could just be client setting though, because I know on Jellyfin you can change the “backend” in the client that it tries to use and can make the difference on things like x265/HVEC playing back or not.
I think the transcode part is decided by the client, but in the Jellyfin server admin you can control if a client can request a transcode (which may not be actually needed - and if you know what client they are running it’s probably easier to decide). This could just be client setting though, because I know on Jellyfin you can change the “backend” in the client that it tries to use and can make the difference on things like x265/HVEC playing back or not.