Qbert

Check out the Tail Scale Guide pinned on the home page of the forms. It's a really easy walkthrough. TDLR, tail scale uses a 'exit node' inside your home where you tunnel into from your devices. It routes all traffic through that exit node that's running tail scale on it. It's very similar to running a VPN or wireguard at your home.

This.: I will add, Ive ran some pretty shitty local Minecraft servers on a Rasp Pi3B with only 2 GB of ram. Now that wasn't modded but my point is, 16 should be fine for now, If you have an issue with the gui and management side of the server I highly recommend using MC Server Soft and just running it on your Windows machine for simplicity.

What Dylan said, your biggest limitation with your server will be the CPU, See plexes guide on the recommended CPU. It should be fine for just 2 4k streams but don't quote me on that lmao. If I remember correctly—and I might be wrong—certain GPUs are significantly better at transcoding than others, so I would look into it. Plex Guide to CPUs for their servers

Wifi is fine but your motherboard has 2.5 Gbe Ethernet networking on it. If you plan to host something like a Minecraft server or a plex media streaming server, based on my experience with wifi 6 and ethernet, I will take and highly recommend ethernet (Cat6/ Cat6a) for anything where latency, stability and throughput matter. For the GPU, the 6600 might be nicer if you plan to do hardware compression or streaming I think it's called - I'm not to familiar with the GPU side of Plex. For the Minecraft server, I can speak to, Minecraft servers are very core dependent so having an 8 core over 4 is a good idea but it depends on how many people you are planning on hosting. I would also like to note that you may need more RAM if you want a higher render and simulation distance as those parts of the server get stored in the RAM and can be quite large sometimes.

This. Also some bios allow you to tune the fan profiles without an os application.

What zerologic said, currently there is no headless install of Hex OS, I would go with put a GPU from your main rig in temporarily and then remove it after install. Or, buy a cheap GPU for like 30$, something like a rx 570 or 980 or something cheap and leave it in there.

^