tl;dr - you will be fine with “base” frequency RAM like 2666 MHz for Coffee Lake or 3200-3600 for latest, second gen Ryzen… and there isn’t any significant performance gain. 10-20% when going from 2133 MHz to like 3200MHz while having strong GPU and CPU present.
The benchmark:
https://rk.edu.pl/en/wow-performance-different-ram-configurations/