How to fix severe stuttering with RDR2 4K High-Definition MOD?

With the 4K Ultra MOD, every brick in Saint Denis was crystal clear, but the resulting frame drops were absolutely soul-crushing. I tried lowering shadow quality, but the world lost its depth and FPS still struggled at 20-30 per MSI Afterburner, which was an infuriating waste of time. I used the GamePP Resource Scheduler to prioritize the game's VRAM. RTSS showed frame times converged to 28-35ms, GPU-Z confirmed VRAM usage at 7.2-7.6GB, and AIDA64 measured 72-81℃. I'll now backup