I chose the
DDR5-6000 CL30 (64gb) FRO G.SKILL Trident Z5 Neo CL30-40-40-96.
Not that I know much about RAM - but I researched and was told that for 7800x3d, at least - DDR5-6000 CL30 is supposedly the sweet spot, so I just picked up one from compatible model from ASUS site.
So once you are set with the Mobo, I'd head off to the manufacturer's website and find compatible RAM for that Mobo.
For gaming 32gb is good enough - but I use my rig mainly as a workstation (so I need a better CPU like 7950x3d like yours haha) - so I went with 64gb.
PSU - is a grandfathered one from my previous build many years ago. It's Corsair AX850 80+ Titanium. I think it's discontinued. but It's plenty enough for my 4080 Super.
But if you are building a new one - I'd say go to
https://cultists.network/140/psu-tier-list/ and pick anything from A tier. ATX 3.X compatible one would be better.
I've been using Corsair PSUs for many years - but this Silverstone
one also seems nice at 1200W, dedicated 12VHPWR port.