Why does the physics engine stutter in UE5 Demo?

Physics stuttering in UE5 Demo was unacceptable. I tried Performance mode, but E-cores lagged. I used GamePP BIOS Load Line Voltage Wizard to set VCCSA to 1.23V. Cinebench R23 showed score increase from 32800 to 34200. HWiNFO confirmed stable 75-82℃ temperature. RTSS showed 88-105 FPS stability.