Conclusion: we do not recommend iGPU Undervolting. If you still want to try it anyway, please keep in mind that iGPU Undervolting has different testing methods and different worst-case scenarios.

How much does it cost to Undervolt iGPU?

CPU Core and CPU Cache should generally have the same undervolt. It used to be suggested to run a modest -50mv undervolt on the iGPU, but there's some consternation about this at the moment. Some have claimed this leads to stability issues waking from Standby and does little to reduce temperatures.

Does CPU Undervolt affect GPU?

You won't damage your GPU by undervolting it, but you do risk losing a bit of stability. You'll have to decide if the power savings and cooler operation is worth the slight risk of instability. If you do decide to undervolt your GPU, stress test it for a few hours to make sure it holds up.