I prefer Jellyfin over Plex. Plex has become too bloated. Jellyfin is free, open-source, and well maintained. I have it running on Docker on my NAS, feeding multiple devices, accessible on every platform I use, and it hasn’t failed me. I was a lifetime subscriber of Plex before I made the switch, and haven’t looked back.
LTT did a great video about Jellyfin. Keep in mind that this video is 5 months old, and they have had updates since.
You can create accounts for Jellyfin that allows people to log in. However, the way you serve it to them is your responsibility. In my case, I set up my system with DDNS to work off a personal domain that anyone can connect to with the correct credentials. It’s a bit more work to set up, but I like it better in the long run.