This is basically what I do. M1 Mac mini with a 16TB OWC Gemini. Chronosync backing up to this server and Backblaze personal backup of the mini, only.
See this thread for the story: https://talk.macpowerusers.com/t/updating-my-mac-mini-server-setup/33210
And you don’t need any more computing power. Mine runs just fine with 8GB RAM with room to spare, and I’m running Plex and Unifi as well. I’ve got 1TB internal because I upgraded from an older mini with 1TB internal and I didn’t what to do any structural changes.
Notice that BackBlaze is using half the RAM, but still no problems.