Hey, I opened my 1500 USD laptop the week it arrived, voiding the warranty

The end of the month i opened it again to put better thermal paste on it.
Still running strong 2 years later.
I would not hesitate to get a GPU waterblock if I was watercooling a desktop rig (if I had the money to do it) the performance benefits are just too good.
As far as running it with less radiator space, judging by the people running the krakens on GPUs, I think you could get away with a single 120/140mm rad as long as it was 45+mm thick per GPU.