Hi,
If you are camping in a truck bed topper, no furnace, TV or microwave, your largest load is probably the CPAP. If you move every couple of days, connecting batteries to the alternator through the trailer connector is sufficient.
If you stay in one place more than a few days, get a single 100 watt portable solar panel with a small inverter. Charge when sunny. Using an electric blanket might require a second solar panel. They are $100 each or less.
I use 2 flexible solar panels that fit under the mattress when not in use and can go three days or longer on two 80 AH batteries without any charging in my TC.
Hope this helps,