I do run a full hard top on my scrambler, so those who run a half cab might have different experiences.
I installed the A/C / heating unit from Jeep Air a couple years ago. I was very disappointed in the heater/ defrost. It didn’t heat the jeep up nearly enough to warm up the cab. I recently switched back to the factory heater/ blazer blower motor upgrade, and bought a new air-conditioning unit that is just A/C (also from Jeep Air). The difference is night and day. My wife and I spent a few hours in the jeep yesterday afternoon/evening, and ran the heater on low to medium. The temperature outside was only in the mid 40s, so it wasn’t that cold. If I would Have ran the heater on high it would’ve cooked us. So my advice would be stick with the factory heater, definitely do the blazer blower motor upgrade, and just install an air conditioner only unit.