What will hell you in that journey: basic understanding of Linux cli (Debian is good choice), docker and docker compose (make sure you understand the concepts of images, containers, networks and volumes) and of one kind of web server (I’d recommend Caddy because it’s rather simple). After that you basically use the often officially provided docker compose files to setup common self hostable services.

Yes, you are correct. Unfortunatly some options and use cases of “regular” are not covered by wg-easy. If you’re behind a CGNAT or want to use dual stack it’s better to learn and stick to basic Wireguard.

Side-to-side Wireguard VPN if you want to keep it simple service wise. Tailscale/Headscale vor Netbird if you want a relatively easy way to set it up and are okay with a bit of overhead.

If you use something like Navidrome to host your own streaming service you can set up automatic transcoding and enable it on your phones streaming client (I use Symfonium). This way I can always access my whole library at any point with it not using too much of my mobile data. But my flac collection is quite big and even if transcoded completely I could not fit all of it on my phones internal storage.