Why does FPS fluctuate during combat in Wuthering Waves on i5?

During high-frequency skill combos, my FPS would drop from 120 to 60, making the combat rhythm feel completely chaotic. I tried enabling High Performance mode in Windows; while P-Cores responded better, E-Core scheduling lag remained, which was very frustrating. I used the GamePP Resource Scheduler to set the game process to Realtime priority and disabled redundant background services. RTSS showed frame times converged to 7-12ms, and AIDA64 confirmed CPU temperature stabilized at 72-78℃. Clock speeds hit 3.4-4.8GHz via HWMonitor, and voltage stayed 1.22-1.35V per GamePP to backup