I'd like some advice on Intel XTU too. I have the G752VY.
Darnassus I think you remember my post about high ambient temperature and my CPU throttling. Although by installing an A/C system and using Notebook fan control with Dreamonic's profile is preventing my CPU from throttling, if I leave Hwinfo running on the background and check it after an hour of gaming I see a max temp of ~85 C and an average of ~76 C.
That max temp is really bothering me and since I've heard that undervolting does not impact performance I decided to hop on the same boat as the OP here.
At what voltage should I start and when should I stop?
The compy can go up to 80, but going above is when it becomes worrisome so yeah.. what's your ambient again? I forgot. I myself sometimes even have days where my ambience is 35-40*C but I've never gone up to 85. Sounds like you have a paste problem. ;x
For Undervolting, start at -50mV and keep going by small increments, such as -5's or -10's. Remember, CPU's are.. practically unique in their build quality. Results differ between machines. ;3