Best Method of GPU Ventilation?

I'm wondering about the best possible method of GPU ventilation in terms of air-cooling. We're all looking to keep our prized graphics cards running at peak efficiency and at the lowest possible temperatures. I've got a couple different scenarios which involve common case airflow designs and I'm looking to find ways to optimize the airflow in each one.

The first setup involves a case which has a solid front, that is, no intake fans blowing air through the case. The only fan that comes with this case is a single 120mm exhaust fan at the rear of the case at the height of where the CPU would be located. The graphics cards are down at the bottom of the case where they vent their exhaust out the back of the case through their own vents at the expansion slot openings.

Now, the side of this case has dozens and dozens of holes all the way from the top to the bottom in a row from roughly where the processor would be down to the bottom where the GPUs would be. These are designed to be the size that a screw would be able to fit through for the option of adding an extra fan onto the side. If I wanted to add another 120mm fan here to cool the GPUs, would it be more beneficial within the context of this case's airflow design to place the fan over the GPUs so that it draws air in through the side holes (let's assume in this scenario that the room temperature is substantially lower than the temperature within the case) and blows the air onto the GPUs, or place the fan in the same location but flipped so that it would draw any hot exhaust from the GPUs and blow it out of the case through the side holes?

The second setup is pretty much the same design as the first, only the front of this case has 3 120mm fans going down the front of the case, blowing a constant stream of air through the case to the exhaust fans in the back which then blow it out. There is also the option here to add extra 120mm fans on the side, right above the GPUs, to either blow air down onto them, or draw air from them and out of the case. Would it be beneficial to add the extra fans on the side? Or, would it be better to leave the airflow alone in this setup? Also, the side of the case could be removed completely and have a much larger room fan placed next to the case, blowing air into it at a very high rate.

Just wondering what those with experience in different airflow setups think about these scenarios. Thanks in advance!