Nice system, I love the Lian Li cases and have one myself. Very nice quality.
Andy what mother board did you get?
There will be some drivers for the mobo to install.
You don't have to buy Windows 10 Pro. It can be downloaded from the MS website https://www.microsoft.com/en-gb/software-download/windows10ISO
When installing just select that you don't have a license key and it'll install but give the occasional nag bottom right of screen. You can then at your leisure buy a license as above. You can add WiFi at any time using a small cheap USB dongle.
Cheers,
DV
I have purchased many many windows keys on ebay. They are perfectly legit, however download the offical installer from microsoft :
https://www.microsoft.com/en-gb/software-download/windows10
You can create a USB installer which is the best and quicklest way to go
I make a USB installer via another machine?
So this ties in with Darths posts above. I make a USB installer via another machine?
We haven't connected monitor/keyboard up yet...what actually displays on initial boot up...old Windows blue screen era type stuff?
The vast majority of gamers still use 1080p resolution, which will be best suited to your video card. More people are going up a step these days, 2560x1440, which your card should manage (but not with the highest settings, as @Alfie says.) Refresh rate is where it's at, 144 Hz being the de facto standard and this is much easier at 1080 resolution. The computer has to work hard to match 144Hz, make sure you have sufficient airflow!
https://www.amazon.co.uk/dp/B07HS7B1DC/?tag=pinkfishmedia-21
So what would happen if we plug it into my 65" LG OLED