Just as @FunkZ said, 3600 is the sweet spot, browse YouTube for games you play.
Normally 16gb 3600 low latency is the best around for most games. Actually, in the majority of games, you'll have more performance with lower latency than going with more capacity.
If you haven't purchased the CPU yet, I would even advise going 5700X3D, not sure whats the budget but I'm assuming not very generous if you picked the 5600X.
Good luck with the build.
The Englishman