Just curious, did you ever find a reason for this? I noticed the same thing, opening high-end duties makes me drop frames for a split second (144 to like 128-131). Even when playing the game, I sometimes get the stutter and it feels just like the PF one. I feel like its a driver thing, but I'm not sure what a better version may be.
Specs:
GPU: Geforce RTX 2070 Super
CPU: Ryzen 5 1600x
144hz monitor (no gsync or freesync)
16gb ram @ 3200mhz
Running on Windows 10