with the latest BIOs Asus has disabled undervolting. Seeing as you have the latest model, I am guessing you won't be able to. I had to roll back BIOs on 9th Gen... Shame.
I'm using it with BIOS Version: G512LW.310 and had the option to undervolt -80... that's how I use it. Throttlestop won't work with undervolting. Only the 'Disable turbo' works. with tha on it's really quiet and cool, even under load.