You certainly don't _have_ to do anything, and under a fixed computational load the Pi4 should run cooler because of the better core architecture. However, you

You certainly don't _have_ to do anything, and under a fixed computational load the Pi4 should run cooler because of the better core architecture. However, you can get better performance by cooling. A fan off to the side of the board blowing between the two would probably work well if you want to keep it on top, but you're probably fine doing nothing as well.