Why does GTA VI stutter during city driving on RX 590 GME?

I felt totally robbed of immersion while speeding through city streets; my VRAM usage climbed to 7.2-7.8GB per AIDA64, causing FPS to jump erratically between 45 and 22. I first tried forcing High Performance mode in the driver panel, but while peak FPS rose, the 1% lows dropped further, making the stuttering feel even worse. I then used the GamePP Resource Scheduler to elevate the process priority from Normal to Realtime. After this, GamePP Sensor showed VRAM controller load converged to 12-18% and core temps stabilized at 72-78℃ per GPU-Z.