Music playlists are different from Plex. You can create them import them or generate an instant list.

4k is seamless and performs better imo. You can use transcoding or not if you have files they way you want them. If you do you can select on a per user basis who gets to transcode.

You can set bandwidth limits.

I've seen a feature to allow multi user streaming the same movie so you ig watch at the same time. I use npm and often a couple peeps might watch a movie at the same time without using this feature and works fine

I use the client app on Android and a firestick atm. I think I just downloaded it but you can side load too if you want. The media server app is available for various os. So technically you could set it up on whatever you want. Just check your app store

https://jellyfin.org/downloads/clients/

It can plug into homebrew or m3u playlists for live tv if that is your suggestion. It has a plugin for nextpvr and tvheadend if you utilize those for over the air or already have an m3u setup too in those pvr services. Those are great btw and available in docker containers.

It always defaulted to what I have my files encoded. It absolutely can transcode to support other clients and you decide preferences. I did notice since most of my files are h.264 with few h265 sometimes it helped to turn off transcoding for me because the client supported it natively. Jellyfin was transcoding h265 mkv to like an MP4. Anyway a quirk

Login is pretty simple. Passwords users can change. Has codes it can generate to approve a new device if you are already logged into an app on your phone. Like 6 temp numbers. Can also setup pins or whatever they call them under users.