Munken-

I once had all kind of problems with installing Windows... Turned out to be a faulty installation media. Or it might be your USB flashdrive or USB port. I would try to rerun Media Creation Tool an a different USB flash drive and putting it in a different port.

Without the error codes it's hard to tell what's exactly going on.
But I'd suspect that the install on your USB drive is faulty. I'd try to create the boot media again, maybe even with a different USB drive.
Also make sure that the drive is empty and freshly formatted

All you need is the media creation tool and your drive. If you visit the same page with a browser that's not reporting as running on Windows you'll also be able to download the iso instead.
You can prepare and install even before buying a key.

Misunderstanding lol.

Not quite. You can either download the Media Creation Tool or an ISO, the ISO will need "flashing" to the USB drive before you can boot from it (something like RUFUS can do that), the MCT will handle the process of downloading Windows and creating the USB installer in such a way as it will be bootable and it does it all seamlessly. Either way you need a working computer to create the installer, MCT is Windows only, macOS & Linux both have ways of doing it too but neither is as simple as Microsoft's own solution.
 
What does this even mean?

The majority of VR workloads shouldn't be of an issue with a 5700XT, would recommend having at least some flash-memory to accelerate the HDD and booting from a HDD is generally extremely slow. A 256GB SSD should be sufficient for the operating system and to accelerate commonly used programs, I will link a good budget-friendly 256GB SSD.
 
Link to Silicon Power 256GB 3D Nand A55 with SLC Cache SATA 3 SSD:        https://www.amazon.com/dp/B075RJS55D?tag=pcpapi-20&linkCode=ogi&th=1&psc=1
 

I am assuming you already own an SSD?
 
Also Navi driver issues have been fixed for a few months now, the RX 5700XT is a good choice!

Don't worry, the driver issues are not really a problem with the new Navi drivers released by AMD. If you don't need ray-tracing capabilities of Nvidia's RTX graphics cards, I would recommend the 5700XT.

Should've included in the original post sorry. I have a Razer Blade 2017

I will really look into this one. Thanks for giving your thoughts.