PSU with bottom/top fan mounted upside down on top of case?

Yes the power supply and it's fan will work when the psu is installed "upside down" (fan on bottom) in the top rear of a case. That is the way it is supposed to be configured. The fan will pull in warm air from the interior of the case and exhaust it out the rear panel.

A long time ago there was a push to standardize manufacturing so everyone could make components that were interchangeable. Intel was the driving force behind what became known as the atx standard. Intel specified the power supply should be located at the top rear of the case because their new cpu's were running hotter and the psu had the only exhaust fan. At the time there were no case fans. That was before the Internet. I distinctly remember looking at pictures in Computer Shopper Magazine trying to find a case with ventilation slots to help with cooling. It's a lot different today.