First my context: I’m also running multiple Proxmox hosts (personal and professional), and havea paperless-ngx instance (personal/family). I tried Firefly, but the effort required to get it to a point where it would be if use to me was too high, so I dropped it. Haven’t used n8n.
For the setup I’d just use the Proxmox community scripts, if you haven’t heard of them. Makes updates trivial and lowers the bar to just trying something to basically zero.
Paperless-ngx I actually use, cause it means I can find something when i need it. It’s all automatically ocr’d and all you have to do is categorize them. With time, it’ll learn and do this for you. You can (manually) setup your scanner to just directly upload files to the “consume” folder and it just works. PC/server power is near irrelevant, it just means OCR takes slightly longer, otherwise it’s a web server. You can run this just fine on a raspberry pi.
I don’t have any real automation setup, so I can’t really comment on that. My advice is to just install it, see what it does and how it feels. Try to anticipate if and how much automation you need. Many aspects of all this are of the “setup once” variety, where once it’s working, you don’t have to touch it again. Try to gauge if the one time effort is worth it for you, then go from there. As I said, it was fine for paperless for me, but not for Firefly (but I might need to revisit this).
You can’t put the kind of memory used in servers (registered ECC dimm) into normal/personal computers. It’s not just that the ECC won’t work, they don’t work at all.
That’s different with unregistered ECC dimms, those will work (at normal spec speeds), but the ECC part will just be unused. These are in the minority though for servers, in practice they are more used in workstations.