The PCH temperature on my Z690-Formula was also high. I made a drastic solution. I took off the LED cover and glued (double-sided tape) a small fan Believe it or not but the temperature of the PCH dropped by 15C (ambient temperature of 27C)
I just removed the plastic logo shroud that covered my Z590 heat-sink and got 8-10 degrees lower. From 75 to 65c at idle, below 70 at load. Only thing is that it leaves the Asus logo LED exposed.
The PCH is responsible for all peripheral devices - Ethernet, storage, USB etc. If you have the voltages too low these devices might not operate properly and may fail or corrupt data. I would tread lightly,
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