The performance boost in Hitman 3 is interesting. Probably results from being able to keep a more consistent clock speed during intensive scenes because of lowered temps
It lowers the temperature of the SOC allowing the CPU and GPU to run for longer periods without throttling. Meaning that you will have more consistent frames and low 1%.
This convinced me to play around with undervolting and I managed to do -50/-50/-40 (cpu/gpu/soc) while still passing furmark and all mprime tests, now I can play Stardew Valley for even longer!
Undervolting aims to keep the same performance at a lower power draw. But because modern SOCs scale their frequency dynamically based on temperature, a lower voltage means slightly better performance
Think of amps and volts like a hose and water. If you put your thumb over the hose the water shoots out faster. Undervolting works in a similar way. So the goal is to lower the volts but maintain or even increase the amps to improve performance.