Why does Returnal FPS drop from 120 to 70 in combat?

In bullet-hell scenes, my frame rate would irregularly drop from 120 to 70, making precise dodging nearly impossible. I tried disabling E-Cores in the BIOS; while drops decreased, the overall average FPS fell by 15, which was a counterproductive trade-off. I used the GamePP Resource Scheduler to set CPU priority to Realtime and forced a High Performance power plan. RivaTuner showed frame generation time converging from 8-25ms to 7-12ms, while AIDA64 showed 65-78℃ and HWiNFO noted P-Core load at 80-90%. Perfect flow!