1. AIO position. Check “BETTER” and “OK”. Why is that? Because OK stops being ok if the pump doesn’t have enough liquid, it won’t reach the tubes, and the pump will be fed with air. This shouldn’t really happen with new quality pumps, but will if given enough time anyway.

2. “Hot air rises” with a speed and strength that is ridiculous compared to a fan moving air. So unless you have a completely fanless system (including the gpu, if any), there is no need to think about it. The reason why the usual flow direction is front to back-top is because people tend to have their PCs under the table (or at least used to) and the fresher air would come from the front side. If you have a different environment can change the fans.

So please, stop repeating “rules” and understand them.

Please, if you comment other things or even disagree, tell WHY. It’s the main reason of this post. To understand the reasons and learn.

Update: “enough time” can be years, so many users won’t experience the problem (which reinforces why Jay said “ok”).