you said : only on certain games ? It look like a chipset problem. SSD to Memory, then bottleneck. You seem to have the money to buy a better motherboard... a 370 chipset ....It seem to me that the drivers are not totally ready yet for the chip sets of this motherboard with Ryzen. ... Check the Temperature of the components also.. I presume that you don't have any hard drives that are "sleeping" ... it take a while before those HDD wake up.
Just my 2 cents.