Several leaked benchmarks suggest that the 3950X beats the 10920X by a significant margin. As for overclockability, you're not going to be reaching Intel-level speeds anytime soon, but the process itself should be relatively similar, essentially just tweaking voltages and clock speeds until you have something stable. No real recommendation for the SSD, just try to get whatever has the lowest price/gigabyte at the time of purchase, and go for NVMe if it's important (Which it probably won't be but up to you).