Regarding the PCI 3.0 and 4.0 Slot, the performance impact is typically less than a few percents going from a x16 PCIe 4.0 to x16 PCIe 3.0. CPU selection often has a larger impact on performance. We look forward to new platform that can fully take advantage of Gen4 capabilities for potential increases.
Regarding specific model, we recommend using fast CPU and Intel i9-10900K is one of the examples of high-end CPU, you can go with fast or high-end CPU for better performance. The system would perform better with a CPU and GPU that are closely matched in performance capability. To ensure a balanced build, your CPU and GPU should be more than just compatible, they should be complementary.
that is what they said
what motherboard should i get for a 10900k?