I'm not sure if it's an optimization issue, however I've noticed I would get lagspikes in full screen for games. I've only tested two games however once I turned off full screen the lag would go away and run smoothly, albeit in a smaller window.
Here's my setup if it matters:
Ryzen 1600 (not oc) with stock cooler
Asrock ab350 pro4 (latest bios)
Rx 480 (reference card)
Hyperx ddr4 8gb 2666mhz