I have tried it a couple of years ago (maybe less), but went back to Plex because of higher polish and family sharing features (which are a little clunky on Plex, but usable). Also, I have PlexAmp set up everywhere (including some Android desktop displays) for music.
How does Jellyfin tackle closed user groups, family photos/videos, remote access, etc?
Look into jfa-go. I run it on the side and it hard-integrates into Jellyfin and adds a lot of account management stuff and the group/policy specific config you're mentioning
How does Jellyfin tackle closed user groups, family photos/videos, remote access, etc?