I've only skimmed the thread so excuse me if I say stuff that has already been said. Maybe you've already bought a new PC by now. WHO CAN POSSIBLY KNOW without reading.
Yeah AMD's better than Intel for CPUs right now. Partly just because they've got better, partly because multi-core stuff is starting to matter more and also in large part because they're not as susceptible to the speculative execution/prediction vulnerabilities that have been discovered lately (and thus don't require the costly mitigations).
GPU wise, last time I looked, AMD's better (value for money) at the bottom end and in the middle, Nvidia's better at the top. Also AMD cards tend to be power hungry if that's a concern. If you're going to be running Linux, go AMD cos their open source drivers are really good now.
For your main drive *totally* go with NVMe for your system drive. They're about the same price as normal SSDs now and *much* faster.
This is pretty much the best one and not that pricey:
https://www.amazon.co.uk/Samsung-MZ-V7S1T0BW-Solid-State-Drive/dp/B07MBQPQ62/
This cheaper one is still going to be miles faster than a normal SSD:
https://www.amazon.co.uk/Crucial-CT1000P1SSD8-Solid-State-Drive/dp/B07J2Q4SWZ/
I've got a mini-ITX PC currently and it's fine. You do have to pick your graphics card carefully but other than that it's been no different to a full-size thing.
And yeah, might as well go 32GB and all that blah blah blah.
Hello.