You will find an .ini file called "adv_options.ini" which you need to edit. The exact location of the file should be C:\Users\\Documents\Call of Duty Modern Warfare\players\adv_options.ini.
Open up this file, and you will see "VideoMemoryScale = 0.85". Note that this number can differ case by case, and is the root cause of the bug. 0.85 is a scaling factor for how much of your available VRAM is going to be used when running Warzone.
For instance, let's say you have 8GB VRAM, and if the scaling factor is set to 0.85, then 8GB * 0.85 = 6.8GB. This means that you're capping the VRAM usage at max 6.8GB, and the rest of the capacity is not being used. Increasing the value may fix the issue.
set VideoMemoryScale = 0.55 and set VideoMemoryScale = 0.65 removed only Stuttering FPS drops