Half of that is the arr stack, some is management stuff, the rest is standalone stuff and not interlocked at all I think?
I’d consider something for authentication (like authelia or authentik) early on, so you don’t have to convert all your services at once but can integrate them when you set them up.
Funkwhale is more of a thing for publicly sharing your audio, not for personal use, even though it might work as well. I think Navidrome is the most popular thing to stream your own stuff.
Generally I’d start with few services and learn your way around the whole stack before firing up 20 compose stacks without knowing what you’re doing.
You might also want to think about a reverse proxy so you can access your stuff via subdomains instead of different ports.
I had to start over anyways, so I choose SSD only. Pricier of course, but I don’t need a terrible lot of space anyways.
When I still had HDDs, they were usually used once a day for backups, and I spun them down after that.
Optimizing power profiles and C states makes a little difference, but planning with efficient hardware from the beginning is the most important thing. Don’t use your old gaming PC if you care for power efficiency.