Why does Horizon Online stutter during multiplayer gatherings?

I felt totally disconnected when my frames plummeted from 75 to 40 during team exploration; it was a complete immersion killer. I tried disabling all power-saving options in the BIOS, but it didn't stop the drops and actually caused idle temps to spike from 38-55℃ per HWMonitor. Then, I used the GamePP Power Plan Switcher to lock the system into High Performance mode and optimized process priorities. RTSS showed 1% lows improved from 32 to 58 FPS, and AIDA64 confirmed VRM temperatures stable at 52-58℃ with voltage fluctuation reduced to ±0.01V.