While it may be tempting to go "mini" and NVMe, for a normal use case I think this is hardly cost effective. You give up so much by using an all in mini device... No Upgrades, no ECC, harder cooling, less I/O. I have had a Proxmox Server with a used Fujitsu D3417 and 64gb ecc for roughly 5 years now, paid 350 bucks for the whole thing and upgraded the storage once from 1tb to 2tb. It draws 12-14W in normal day use an…
I don't really understand the general public, or even most usages, requiring upgrade paths beyond get a new device.
By the time the need to upgrade comes, the tech stack is likely faster and you're basically just talking about gutting the PC and doing everything over again, except maybe power supply.