I ride at my "naturally selected cadence," and it is not a number. It is determined by a variety of factors that change by day: energy level, average grade on the route, what heart rate zone I'm shooting for, etc, etc. So some days it's 75, some days it's 85. Every once in a rare while, it will be near 90. It's not something I pay attention to while riding, it's just a metric I track when looking at rides overall.

I personally have not noticed a difference in heat output at lower vs. higher cadences when climbing grades, unless we're talking about much lower. My standing cadence while climbing tends to hover around 60rpm, and I often use periods of standing to cool down, as high rpm on steep grades is making more watts, and more power to the pedals means more heat... so I can definitely see something to it.

...but I tend to use "soft pedaling" to combat overheating. Easy, even cadence (very light pressure on pedals) try to maintain an even speed at or above 15mph and let evaporative cooling do it's thing. I have absolutely noticed that dropping below 11mph, it gets real hot, real fast. So for some hills, a squirt of water from the bottle, directly into the helmet vents, seems to do the trick.