It totally depends on the game.
MSFS at 4k, 10700k is 15% faster than 3900x, and in RD2 4k it's 10% faster.
In fact watch this pcie3 vs pcie4 review. Aside from pcie scaling, it unintentionally shows the results of 10700k at 5.1 vs 3900x at 4.5. If I'm not mistaken, 3900x is a little faster than 3700x.