Did you check that you're actually allowed to build and live there? Depending on where that is (i guess left out on purpose), you can't simply decide to build a house in a field.
Java edition is easy to selfhost, did it as a docker stack a while ago. Apart from that, it really depends on what addons etc. your players are usually playing. Most things can be done with not too much effort, but that's probably the thing you need to find out.
Don't use external drives as non-temporary storage. Backups etc, fine, but not as a replacement for internal storage. It will only lead to headaches at some point. Especially as you have one extra slot.
So your native nginx process covers ports 80 and 443. which ports does your NPM use? Are you trying to use the same ports? Because that'll most likely clash.
Good question. I haven't really tried that yet, most of my media plays natively, sometimes the audio needs to be transcoded, but that's done by the CPU.
I moved from a 2700x to a 5700g. iGPU and faster than the old one, but compatible with my old mainboard.
My advice is to put all the server-y stuff on a server and use other machines for the rest. Far easier to keep that stuff separated, although you need an additional machine.
What a load of BS.