You need more than 64 GB of RAM these days. Some of the Epic demo scenes fail the export correctly unless I turn off all other programs while doing it on a 64 GB system. For “real” development, I’d suggest shooting for 256 GB. Also, Something in the 16-32 core range is good for the CPU. When/if the RTX 3080 20 GB comes out, get that; else the RTX 3090 and its over-pricing is pretty much the only good option 
(I’m a fan of AMD CPUs, but not AMD graphics cards – their drivers have always had more bugs than NVIDIA for me. If you’re going to release a game, you’ll need one of each brand of GPU, though, for testing. But maybe that’s a concern for later.