So I use pbo on 9800x3d, 1x scalar ,+200 clock boost, -30 under voltage and I heard something named clock stretching when doing too much under voltage which effective clock speed is lower than reported,I am new so I am not sure

this picture is the stats when Im playing valorant

In hwinfo,is "Core clocks" the reported clock speed and "core effective clock" the effective clock speed?

Also how does clock stretching lower perfomance cuz I saw my cpu is stable at 5425MHz while gaming or what stats should I be looking to? Thank you for any advices