I've considered whether or not case manufacturers really do real world tests for things like optimized placement for a CPU, PSU and mobo. I'm sure they do to some degree, but, for example, do they take a prototype case and place ambient air temperature gauges at say 9 different point inside before actually producing them? And does it even make sense to do so?
Imho, watercooling is a hobby in and of itself lol. Some people do it and some don't, just the same way some people build PCs and some don't. But w/c is often very expensive and mostly unecessary for most consumers, though probably essential for some gamers.
Re HSFs, although my reasoning could be wrong, I would think that a perpendicular mounted HSF would be more efficient than a fan mounted on top of an HSF in general. Theoretically, you are monsterously enlarging the size of the heatsink (assuming your thermal paste is doing an excellent job) and then blowing air from the heatsink toward the back of the case. I think a typical push/pull vs push alone is about 1 degree or something like that. So, this involves a monster heatsink, which helps dissipate heat more efficiently right? Then the hot air gets pushed toward the back of the case, which is better than on the mobo right? Sounds like a good idea to me