You currently have both machines right? But a kill a watt and tinker with it for a bit.
The newer generations get more and more power efficient so there is a good chance you’ll save money. Definitely will want to pull a proc though. You can also buy lower power CPUs on eBay for super cheap too. Then if you ever need the horsepower you can throw one of those back in. And the second one if you need it too.
Depends on both the model and your expectations.
Some models support hardware transcoding so Plex/alternatives work just fine on them.
If you have a model with a couple GBs of RAM then the world is pretty open with Docker containers.
The CPUs are fairly slow though so game server hosting and anything high speed is a no go. I mean, it’ll “work” but you probably will be wanting for more.
I had nothing but problems with xcp-ng. Networking never wanted to work quite right and when I did get it working it would break after a while. The UI is awesome. The clustering features are pretty intuitive.
Proxmox UI is also pretty intuitive but far from pretty. I use the hypervisor as a tool though so I don’t care about the looks. Proxmox has been super stable both clustered and unclustered across multiple sites for me. I’m very happy with it.
NVMe is a technology. M2 is a connector type.
If you open one of those drives you’ll find NVMe tech. You won’t find M2 connectors.