Njay: I think I know what warms up more in the drivers. It must be the transistors that pull the N-FET up (to turn on), Q3 and Q8 in the schematics.
When it’s ON, pumping current into the capacitor that is the MOSFET gate, is dissipates a lot of heat because it is being fed from the battery voltage on one side and at most 12V on the other, capped by a zenner diode. Usually FET driving circuits are supplied with a voltage that is matched to the gate turn-on voltage, so they don’t stress out too much, but here I had to invent this adaptation.
When time permits, we should try putting a resistor or zenner to lower the voltage before the transistor, so that the heat is lost outside of it. We should divide (the power) and conquer (the heat).