Am I about to make a mistake?

Probably not. I've been a longtime Linux user/admin and I like to get under the hood with storage and networking.

Nothing wrong with proxmox at all, I used it for almost a decade.

Most likely not. However, proxmox is a bit strict here and there on how it wants drives, networking and other stuff laid out. Also the hypervisor itself is quite strictly only for that. So, if you want to tinker with something without virtualization platform or use your drives for something else than just proxmox-installation it's likely not officially supported at least and might cause some headache or even bigger problems, like potentially losing data, if you run it in a way it's not meant to.

However, if you just want a pretty capable hypervisor and run all your stuff on top of that it's perfectly fine, specially for hobbyists. For bigger enterprises it has some issues and management for a bigger server fleet, at least for now, isn't as polished as the 'big players' have, but, again, for home gamer it's pretty good solution.

Agreed.

I don't mind paying a reasonable price for access to SSO, especially if the service is fully provided by third-party infrastructure. For something that is fully self hosted on the other hand, a recurring cost for what should be a basic (or at most a one time reasonable fee) feature feels egregious.

Good to see that site is getting updates again.

No it doesn’t. Popularity contest only.