Big ryzen is a good choice.

My home rig is a Ryzen 1900, with only 8GB RAM. It's way faster at OE yocto builds than the i7 at work that has 32GB RAM installed. My 8GB rig does not use swap space while building huge images (like satellite receivers and full-blown XFCE desktops).

For the CPU, the more cores the better. OE loves cores. Real cores are better than SMT cores (a.k.a. hyperthreading), and AMD's SMT has more effect than Intel's.

Harddisk speed has very little impact on your build time. It helps with the "setscene" parts, but doesn't affect actual compile time at all. I recall someone did a build from RAM disks only on a rig, and it was only about 1 minute faster on a one hour build compared to rotating disks.

SSD or NVMe doesn't make much difference. If you have budget to spend, spend it on RAM and CPU but not on disks.

I'd go for a reasonable NVMe disk, mostly for storing and booting the OS itself.

If you plan to share sstate-cache and downloads from this machine to other clients, I'd even suggest a plain big (4TB or so) rotating disk for storing that kind of stuff.

Again, don't spend your budget on disks. Disks are way easier to add later than any other component.

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Mike Looijmans