I am curious what apps you have found really push the 2018 / 2020 iPad Pros hard. Thermally, ect. Or can they handle pretty much anything available? I personally have never experienced any extreme heating up or throttled performance.
Actually charging heats up the iPP sufficiently. Also ProCreate. I am not sure that it can put it to the max but I can definitely feel the heat when working with it.
really try editing a 10-bit 4K HDR H.265 video file. in Lumafusion
or try running a Game called Black Desert Mobile, at max resolution and max FPS it’s really demanding and your iPad Pro will heat up like never before.