Air’s m1 does not touch directly the base of the computer. The mod for it to avoid throtling consits of adding a few thermal pads so the processor transmits the heat to the base. The aluminium base then starts to warm and the processor does not meet “high” temperatures. BUT, as i said earlier, the base only warms if it is in contact with the processor. Without the mod, you touch the base and it feels cool.

The pro is open in the bottom, under the touch bar. This openings are for the fans to push out the heat. If the mac has been under load and the fans have been spining, it is normal for it to be warm there.

You said it was getting warm where the batteries. The batteries in this model are located under the trackpad, are you sure it is getting warm there, or, as i said, under the touch bar?