Work great for PWM fans .. well, most PWM fans. There are a few that don't like having the PWM signal split between more than a couple fans.The PWM lead from motherboard is only a signal going to the PWM fan's PWM PCB. This PCB translates the signal into 12v power pulses to fan motor. These 12v pulse are what control the fan's RPM. The amount of time the pulses are on versus off determine the fan's RPM. If PWM fan has no PWM signal on pin-4, the fan will run on...
GPU airlfow is the other way. GPU draws air in through it's fans, through cooler, against PCB and out in case. This means using the bottom as intake to supply air to the GPU.
Not all case vents need to have fans in them.
So bottom and front intake with everything else exhaust. Remove unused PCIe slot socket covers to allow airflow past GPU and out the back.
I'm kinda busy right now. The key is to try different combinations and see what works best.
NH-D15, R1 Ultimate and PH-TC14PE are at leading the pack, with Silver Arrow IB-E, HR-22, NH-U14S, Archon IB-E, NH-D14,TRUE Spirit 140 Power, Medusa, K2 / Assassin, etc. nipping at their heels .. followed by the pack baying for blood close behind with Megahelms, Armageddon, True Spirit 140s', Megun, HR-02s' & Machos', Ultra 120 Extreme, Matterhorn, etc.