Overheating are generally associated with parking guard use, for the camera to just wake up and start recording when you go for a drive on a hot day, that should not be a problem.
At least i cant say i have noticed that issue with any brand, at worst extreme heat can occasionally get the focus to shift in the lens, but nowadays thats not so bad with quality cameras, in the old days it was more of a problem to be aware of.
If you do want to use parking guard, then systems where you can hide the main heat generating part out of the direct sun will probably fare better, but there are not many dual remote systems to choose from yet.
And it is just a hunch on my part, i have not seen anyone compare a traditional system VS a remote system in regard to heat endurance, but my logic say even if a car get blast furnace hot, then the camera not sitting in direct sun will be much better VS one that do that.
Sadly all the brands that do make remote camera / cameras systems, they have not taken advantage of the fact that the main body you hide somewhere, it can pretty much be as large as you like and so house actual cooler VS the standard dashcams that have a little passive cooler trapped inside a more or less ventilated black housing.
I would not mind if the main unit was the same size / volume as 5 - 6 CD covers on top of each other, if that additinal space was used for cooling and so you could also do even higher bitrates too as the cooling would allow for the SOC to give all it got.