The best type of air to demist is HOT DRY air.
So best is FRESH Air, AC on, Heater on FULL, airflow to the defogger outlets at base of windscreen .
Second best is RECIRC air, AC on, heater on full to defogger.
If car gets too hot for either setting, keep the AC on, turn down the heater setting for temp, but keep fan at MAX.
Outside air has less vapor content. The AC will reduce moisture whether inside or outside air is used. Heater will raise temperature to increase evaporation from the windcreen and thus defog it quickly. Maintaining a high fan settings will also keep side and rear windows much cleaner.