Thanks for the suggestion and great observation. The top fans don't kick in until needed (Asus fan ai)Great to see All Noctua fans build!
You can cut down two fans: The first top mounted which sucks away the fresh incoming air and the third cooler-mounted fan. The third fan might provide a 1-2 degree lower temps but if no gap is provided it creates a buzzing noise on full tilt.
(Also the gpu sag...)
The 3rd CPU fan is just there for looks but Oh DAMN I now know the reason for humming - thanks mate.
Yeah im torn between putting the gpu bracket or not. But I guess will put that sometime
Thanks again @Alucard1729