Heat pump (CoolCat) stops producing heat when outside temp gets down in low 40s. Been there, done that, got cold. And of course you need shore power (and 12V DC for thermostat) to run it.
Heater produces hotter air, but doesn't circulate heat as well. With either CoolCat or heater, I crack the overhead vent open to help air circulation. Heater needs 12V DC from battery or converter, draws about 3 amps to run heater fan. And propane to create the heat.
If heater has never been used before, you will get an oil smell as the oil coating from manufacturing burns off.
DW fitted us with warm blankets, we now set thermostat to 55 (or off) at night.
2019 Flagstaff T21TBHW A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time