Why do I get memory scheduling lag during massive battles in Total War Warhammer III on a Galax B760M D4?

Seeing tens of thousands of soldiers charging across the screen was an absolute rush, but the micro-stuttering was killing the vibe. On the Galax B760M D4 White Phantom with 3200MHz DDR4, the memory controller timings were jumping wildly between 16-18-18-38, causing 12ms - 18ms of scheduling latency when the CPU processed massive unit AI. I tried enabling Windows Game Mode, but while the average FPS went up by 3, the 1% lows were still garbage—not acceptable for a hardcore setup. I went into the BIOS, switched memory presets to Manual, and crushed the tRFC timing from 600 down to 520, while bumping DRAM voltage to 1.38V. RivaTuner showed the frame time variance shrink from a chaotic 22ms - 35ms down to a steady 14ms - 18ms. I actually blue-screened upon entering the game the first time I tightened tRFC, but backing it off by 20 units made it rock solid. VRM temps stayed around 58℃ - 64℃. Confirmed the mode switch via the BIOS panel, and frame times are now a consistent 14ms - 18ms.