1 and 2 are easily handled with docker apps, you would then want to get you a cheap (or free) domain and reverse proxy those services through said domain. There are multiple threads on this on the forum. A domain, can be either super cheap (mine runs me about $12/yr) or you can get a free one at duckdns... the end result will be the same.
1. Navidrome... Very easy to set up
2. Nextcloud. You'll have to set up external storage for files that aren't in the nextcloud database, but that shouldn't be a problem. Multiple apps are available for it (NC Office, Photo apps, etc.) that should handle all this.
(A thread dedicated to setting up Nextcloud through duckdns with swag.. Post #4 would be the "guide")
Thread
Nextcloud Bad Gateway
I setup Nextcloud using the docker compose file from this tutorial:
https://youtu.be/aemqzgNbMPg And I followed the steps from Techno Dad Life here:
https://youtu.be/4HPXGKfFibc Both tutorials are very similar. I've tried to setup Nextcloud twice now and both times, upon completing the tutorial I get "502 Bad Gateway" when I attempt to go to my DuckDNS url. I've searched around for other solutions but I haven't found one yet. Thanks in advance for any help.
Once you have NC working, routing Navidrome through it is a snap.
https://www.navidrome.org/docs/installation/docker/
3. I'm not a Windows user, but I don't really backup my laptops. ALL of our data (music, photos, etc.) are on the server.. so.. I mean I could lose this machine right now.. and other than the inconvenience of replacing it and then reinstalling and setting up my Linux OS of choice.. I wouldn't lose a thing.
4. I hate RAID... it just seems to cause more problems than it's worth.
I have a 4 data drive system (OS is on a flash drive)... Basically Disks 1-4. All are the same size. I have simple Rsync jobs that back up Disk 1 to Disk 3, and Disk 2 to Disk 4... they run once a day, and I don't worry about it.