Docker is a game-changer for managing upgrades. I don't do a ton of audio books, but I have a pile of photos, ebooks, video, and a music collection going back to the mid 90s. Hosting my own wiki as a knowledgebase is super useful. Same with Readeck for remembering the things I read.

I use tinc to access the box from wherever, which lets me use the wiki while out and about. It's like wireguard, with smarter routing. If I am at home, I get a direct connect instead of going out to my vpn server and then back in to my home to reach the NAS. Tinc is a pain to put on a phone, though. Wireguard is much easier to setup and maintain on mobile.

For back up, borg-backup is pretty great, but for low-value data (e.g. popular media) I just rsync a copy somewhere periodically and call it good enough. Tinc lets me put a box offsite and back up to it pretty easily. If you want something more commercial, Backblaze is solid and inexpensive.

I've never used a commercial NAS box, just generic linux boxes with lots of drive bays. There's something unsettling about depending on Synology not to forget who their customer is. For most things I want to do, that's good enough, though I am probably missing some ease-of-use features I don't even know about!

Good luck with your #homelab!