I'm about to buy some other fans for my H100 cooler and I was thinking about the best way to mount them. I currently have the fans as intake fans, as it seems to be widely recommended - but I'm unsure if I should place the fans below the radiator (which is how it is shown to be installed in the Corsair manual/quick guide, but it doesn't mention if it's different based on wether the fans are taking air in or blowing out - the direction is not specified) - or if the fans should be between the case roof and the radiator?
When it comes to radiators, coolest air is always ideal. However, the air exiting the radiator isn't going to be that 'warm', so don't let airflow direction really be a big hang-up. The reason liquid cooling and better yet, real watercooling work so well is due to the much larger thermal capacity that water-based coolants have over air. They have the ability to absorb and transfer more heat, more quickly from a heat source which is why this kind of cooling excels when given adequate flow and radiator space for the heat source being cooled.
If your case already has good airflow, you shouldn't be worried about which way the fans on your rad are moving air or worry that the air will be anything more than lukewarm at most.