How to stop severe stuttering in Novigrad markets for The Witcher 3?

I was devastated when walking through the Novigrad market; the screen would jump violently, making combat feel sluggish and ruined. I tried enabling Windows Game Mode, but frame rates still fluctuated between 45-72 FPS per MSI Afterburner, which didn't touch the root cause. I then used the GamePP Resource Scheduler to force the game's main process priority to the Realtime level. The results were night and day: frame times dropped to 11-14ms per FrameView, and CPU temps stayed at 62-68℃ per AIDA64, while fan speeds hit 1200-1400 RPM per HWiNFO.