I have deshrouded the GPU. The GPU is undervolted (1874mhz, 875mv), the CPU is stock.

After some testing on fan configurations, the best way is to use bottom fans as intake and fuma fans as intake too (reversed).

The temps are as following :
CPU 100% fan speed, prime 95 small FFT 30 minutes : 34c delta
GPU 100% fan speed, superposision 1440p all maxed (GPU load 95+) : 38c delta

Of course, i don't run the system full blast, with a quiet CPU and GPU curves, temps are as following in a 24c room (2h of call of duty campaing gameplay then a game install who spiked the CPU at 100%):
CPU max 74c (temps of prime are lower because the CPU lower its voltage and clocks to stay withing reasonable TDP without spikes)
GPU max 67c

The funny thing is the GPU is quieter than the CPU and the CPU is cooled by a fuma 2.

Oh and the system works without issue with a 600w corsair platimun PSU. I even played 30 minutes of half life alyx and the headset was powered through USB without any issue.