Yes, we have extensively checked to make sure our settings are the same. I have even set my system to run at 2560 x 14440 even though my monitor supports 3440 x 1440 ss we are running the same resolution. Same thing happens in Heaven and 3DMark.
I have 3 x 140mm fans at the front, and 4 x 120mm fans exhausting air through my 360mm rad and through the back of the case. I don't think airflow is an issue here. I have set my system to calibrate the fans and temperatures in BIOS, and the fans hardly ever ramp up their RPM because the case temp never gets very high unless I am benching the CPU and GPU at the same time.
His case is using a 200mm fan at the front, and three 120s in the top and one in the rear. His case is a little smaller and had drive bays which my case doesn't have. So, the airflow should be a little better in my case.
I am going to try the GPU fan curve and see how much that drops temps.
It's not a desperate issue or anything as 66c is fine for gaming, but it would be nice to drop it further.
As I did write, from my guess, even how paste was applied (stock) or how really proper pressure is applied on cooler to chip, can play difference in some degress.
custom fan curve shoud bring temps down, on expense of some noise (for me, it is not much noise).