CPU: Threadripper 1950x was on sale.
MB: Cheapest x399 board with two 16x PCIe.
Cooling: Thought to try air cooling first. If it doesn't work out, go for liquid cooling. I used the 6mm clearance in Noctua. Slightly difficult to screw two threads over cpu on mobo. 3mm should be enough!
Video Card: Got RTX 2080 Ti. Will add another later.
Storage: Two NVMe SSD. Both work at advertised speeds after installing Samsung drivers.
RAM: Initially, tried the CMD32GX4M2C3200C16. Windows 10 worked well at 2666. Returned it because I read only Samsung b-die is stable at 3200. Got the low profile 3000 version. No issues.
Notes: When installing Windows 10, I disabled IOMMU on the bios.