No need for virtualization (so no Proxmox, TrueNAS, or Unraid) Run lightweight containers for web services like Immich, Paperless-ngx, Pi-hole, and custom services I’ve developed
Do you not consider containers virtulizations? Or do you plan to run your webservices in the same context? Because I would really suggest against doing the latter.
However, I’m unsure if I really need RAID since I’ll perform regular backups.
Raid is not a backup anyhow ;).
If you don't need the capacity or redundancy of raid I would suggest you buy a single >=8Tb drive. It should be a bit cheaper (For example, I recently payed ~270€ for 16 Tb, which I'd reccomend over paying 240€ for 8Tb in total. There are probably also 8/12 Tb drives for less then 240€.). It will also use half the power as that does not really scale with capacity.
Edit: there are a bunch of 8tb drives at 180€ here for example.
I don't think ssds would be viable with a total budget of 500€ and the need for >=8Tb of storage.