Planning to build a home server

Hi y'all! I'm planning to build a server around i7-8700k. I do have a Windows 10 "server" with i5-3470 for NAS and Plex for now, but got a good deal for 8700k, z370 and 16gb (2x8) of ram. Going to use unRAID as the OS. There is going to be a 2.5GbE connection between my pc and this server.

Parts I have already: i7-8700k, MSI Z370 Gaming Plus, Corsair Vengeance 2x8gb 2400cl14 kit, 4tb WD Black, 4tb WD red plus, Usb stick for unraid, 550w psu, Fractal Design R4, Cpu cooler

Parts I don't have: 2.5GbE PCIE network card 256gb m.2 nvme ssd cache drive

The server is going to be used for 1-2 Minecraft servers, maybe Assetto Corsa server, Plex 1080p 1-2 streams, NAS, maybe pi-hole, qBittorrent with NordVPN (openvpn?)

If you spot anything I could improve on before building this, let me know. I know that the hardware I have is overkill for the stuff that I'm going to run on it, but got it for cheap. Might upgrade the memory to 32 gb at some point. Might also add two 4tb or 8tb drives if I need them.

Other 4tb is going to be parity.