Listening to music from plexamp on my phone when I'm out of the house?
Would you still be able to do this if you put plex behind tailscale and connected to your tailnet on your phone?
Normal Plex works using that way, so probably.
Probably? But then I'm using the "vpn slot" on my device all the time which prevents me from connecting to my work VPN when I need it without a little vpn disable dance.
And anyway it drains the battery; and maybe I don't want to add VPN to every device I want to listen to music with, like my PC at work.
That doesn't require public internet, you can and should use a VPN for that.
Friends and family connecting to my Plex, all non technical people.
Yup. Same use-case. I ended up with a geoblock as a mitigating control. Doesn't fully prevent these types of things, but alleviates the mass-scan type attacks.