I should add that the frametime spikes generally don't exceed 60ms, sometimes 100ms and only very rarely 200ms or higher and that only really happens when turning around in a new area or similar. Still, going from ~17ms frametimes (~60 fps) to a sudden 60ms (~17fps) is very jarring.

I'm gonna install the game on another computer with a Ryzen 1700 CPU and DDR4 RAM @ 2400 MHz and see how it runs.