Desk pc case airflow

[Niruvius]

Hi i plan to build desk that i would use as pc case. My concern is how airflow will work in case size of it is 1200x650x200mm. Are 4 fans for intake and 4 fans for exhaust enought i plan to use watercooling for cpu and gpu (3 rad fans total) do i need more fans to take air then? And is it safe to have psu nzxt 750w (not sure about full name) to have both intake and exhaust air from inside the case. Do i need metal tray to hold my motherboard?

[FireCatch13]

8 fans total for air flow is more than enough as long as you don't have anything blocking them, especially considering that the cpu and gpu are going to be water cooled. Most of the heat is going to be generated from the CPU, GPU, RAM, and PSU, but because of the water cooling on the processors and the included fan on the PSU, you shouldn't have to worry at all. As for the position on the PSU fan, I'm not sure what you mean by "both intake and exhaust," but the holes back of the psu usually goes out of the case (as exhaust) and the fan pulls the air through the actual unit. In terms of the metal tray, yes you would usually want to put that in, even with the motherboard standoffs. I hope this helps.