Regarding boards for 3950X, you can compare them here:
https://docs.google.com/spreadsheets/d/1wmsTYK9Z3-jUX5LGRoFnsZYZiW1pfiDZnKCjaXyzd1o/htmlview#gid=2112472504The choice between X470 & X570 is mostly about how long-term you plan this as workstation. The price difference isn't that big, so I would just go with X570.
With the above suggestion to buy top-tier Gigabyte... if you enjoy wasting money maybe. 16+3 power phases are nice, but we are talking 16-core Ryzen, not 32+ core Threadripper. It's waste of money in every single way. 700 Euro boards for 900 Euro chip ? My top-level 2990WX boards were 600 Euro (both with 16+ power phases).
Entry level Asus boards are good choice because they have all good VRM, STRIX-E, TUF,..They have 6 doublers (12 power stages), or 6 doublers + 2 PCH power stages. Basically 12 or 14 power stages, more than enough for 3950X.
For 32GB memory dimms, I would buy the Corsair Kit. Buy the 3000 CL15 2x32GB, it's the best rated option available. In future, when you buy another, it's questionable if it will be able to run at 3000 CL15 as well..but it's still the only choice you have.
My choice for suggesting used 1080ti still stands. I recently upgraded every workstation we have with Quadro RTX 5000 because we need 16GB Vram in office...FOR VIEWPORT ! :- O so I can't image living with 8GB. And surprise..the viewport is same speed as 1080ti (RTX 5000 is equivailent of 2080 non-Ti).
So until GeForce 3080ti with 16GB memory comes along, the current choice is waste of money outside of GPU rendering. If you do GPU rendering, get 2080ti, but non-ti versions (basic and super) are poor choice. 8GB is too little for anything, I can eat that up in Photoshop alone.