if the liquid cooler is cold plate made of copper - it will work.
BUT:
deliding the CPU usually means replacing the TIM between the CPU die and IHS with liquid metal. And using normal thermal paste between the IHS and cooler.
putting liquid metal on GPU is:
1. very risky.
2. kinda pointless as the improvement is within couple of degrees.
Have no idea why you want the lowest possible temps with undervolting.
If you try to lower TDP - just buy more power efficient parts.
If you want to save on electricity bill - it will take long time to compensate the cost of liquid metal (assuming you won't break anything in the process).