Think I may have found the reason for the huge spikes in FPS...and you're not gonna like it

For me, when Windows Defender kicks in it causes my CPU usage to double.

I have disabled Windows Defender and “I am still getting this high CPU usage” even though it is not active (see screen print). I have not messed with the LOD slider yet.

See the Antimalware Service executable at 2.8%. When it fluctuates up then the CPU usage doubles and GPU goes down too half.