What push or pull setup in my case?

[Spev]

So I'm working in the Phanteks Enthoo Luxe: 

 

 

So I have a Alphacool 360 rad on the top of my case, it's 45 thick. Now as you can see in the pic there is space for fans up top, my rad is too thick to fit up there, so that's where I have the fans. My rad only comes with screws long enough to mount it with fans attached, so I can't just mount the rad solo and attatch some on the bottom, which sucks, maybe I can buy some. I would have to do push/pull to get it to be attached to the case... But what I'm trying to figure out is how I can best set this up. Right now I have 3 120 fans on the top exhaust pushing out the top. But would pushing air out of the case or pushing in air be better? Compared to pulling. 

 

There's also this. I don't know what decoupling is, so I'm not sure what the slightly longer screws are for: 

 

[thir02]

i dont think it will make much of a difference, but negative pressure in the case will build up dust

heres a video by linus, should be enough to answer your questions.