How to fix FPS fluctuating between 70-120 in Delta Force?

In intense combat, my FPS was swinging wildly between 120 and 70, making precise pre-aiming nearly impossible. I tried lowering in-game shadow quality; while the average FPS rose by 10, the frequency jumping persisted, feeling like a superficial fix. I finally applied GamePP Power Plan Switcher to lock the system into High Performance mode and disabled CPU core parking. The result was night and day; RTSS confirmed frame times dropped to 6-8ms, and HWMonitor showed fan speeds stabilized at 1400-1600RPM.