For backup and sync I use Syncthing. I can specify which folder on which devices I want to sync to which folder on the server.

I use a folder based gallery on my phone so when I move stuff around on my phone (or on my server) it gets replicated on all my devices.

I also have a policy to sync specified folders (and subfolder) with my family’s devices. No more " hey can you send me all the pics from the XYZ trip"

We take a trip. Make a subolder for that trip in a shared folder dump all our pictures there, get home and open the folder on the computer and prune together.