People tend to overbuild their home system.

You can start small and as you gain experience and maybe add more servers in docker you might want to upgrade. I.e. I was file hosting on a pi4 and external drive for years with no issues. (Upgraded hardware later for Immich)

And you will want Immich (in docker ) for replacing Google photos.

But since your workload is low a NUC or small form factor PC would be fine, as long as it has space for how many drives you plan on adding. You won’t need high end computing.

OpenMediaVault was great, and made some stuff easy. But now I just use Tumbleweed and docker for more flexibility. Any Linux distro will be fine, you don’t have to use a NAS based OS, unless it has certain features you would find useful.