Why does my TEKKEN 8 character lag during melee combos on Huntkey Blizzard T620?

I was losing 3v1 melees in TEKKEN 8 because the Huntkey Blizzard T620 Colorful PSU was causing 0.12-0.18V ripple on the 12V rail, which GamePP Hardware Sensor confirmed as the source of input lag. I tried tweaking Windows power options manually, but the frame generation interval still fluctuated between 8.5-11.2ms, making my combos feel sluggish. Using GamePP Hardware Sensor, I switched the power plan to High Performance and enabled CPU undervolt in the BIOS. This stabilized the voltage curve, reducing the ripple significantly. Now, GamePP Benchmark shows the frame generation interval locked at a tight 5.3-6.5ms, and the PSU temperature stays cool at 45-52°C per GamePP Hardware Sensor.