Jason,
We live in Texas. We have never winterized in the 8 years we've owned our coach. I depend entirely on using a combination of small thermostatically controlled electric heaters PLUS the two stock propane heaters. This has worked well in TEXAS winters, which as you say are not normally too severe. But, we did have that little "cold snap" last winter that tossed the Lone Star State back to the Ice Age, so stuff does happen. Anyway, our coach survived even last winter's deep freeze in perfect shape.
Here is my electric heater setup:
1. One small heater on the dash to warm the windshield. Helps prevent condensation on the inside glass. No thermostat - I turn ON and OFF manually as required.
2. One small heater on the floor in front of the driver seat blowing toward the firewall. Keeps the Allison ECU warm. No thermostat - ditto above comment.
3. One medium heater in the kitchen area. Thermostat control - turned ON all the time it's cold.
4. One medium heater in the bathroom. Thermostat control - turned ON all the time it's cold.
5. One medium heater in the wet bay on the curb side (water pump compartment on our coach). Thermostat control - turned ON all the time it's cold.
6. One medium heater in the wet bay on the driver side (where the water faucet and dump connections are located). Thermostat control - turned ON all the time it's cold.
Our coach is plugged into 50A parked at our house. I'm sorry to say it sits outside totally exposed to the weather (coach abuse). I keep all the electric heaters set on low fan speed and adjusted so they come on at about 55 degrees F. I am sure they must occasionally be all running simultaneosly, but have never had any problem with the combined amp draw popping any circuit breakers.
My propane heaters are set to backup the electric heaters. I keep them turned on all winter, with the (mechanical) thermostats set to the lowest setting possible, which is roughly 50 degrees. 90% of the time most winters the electric heaters keep the coach above 50 degrees. In severe cold, or if we lose grid electric power, then the propane heaters will (hopefully) kick on when coach interior temps drop below 50 degrees. I test run the heaters once a month in the winter to be sure they are functioning properly. As I said, this routine has always worked for us.
We do not travel in extreme cold months or Arctic conditions, so I have little experience in that regard. However, if we did I would just use the same system on the road. If plugged in, I would run the electric heaters. If dry camping, we'd use the propane heaters. In a emergency situation, I would kick on the generator, fire up the big engine, and use every heat source available (including dash automotive heater).
On our coach, only the rear propane heater is ducted to the wet bay area, so obviously it must be running to keep the water pipes and holding tanks warm. There might be times when the interior of the coach would be too warm to kick the rear propane heater on, but at the same time the wet bay might get too cold with the propane heater off. I don't know if this is a common problem.
Link below to the "small" and "medium" size heaters I use. Many different brands and sizes available in this product category - look around online and take your pick.
Lasko 200W MyHeat Personal Desk/Tabletop Space Heater with Simple Controls,...
Amazon.com: Lasko 754201 Small Portable 1500W Electric Ceramic Space Heater...
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Topic: Random Questions on Heating