This year, I too have been put on a CPAP machine. I have only been camping a couple of times since I began using it, so limited knowledge using it while camping. I think the typical use of a CPAP machine in a TC is different than in other RV types due to the type of camping we do. We often dry camp, with no hookups, and probably smaller battery banks than other RVs.
My machine is a 120-v unit. I use a 100 watt inverter, and see no need for the 12-volt adapter. I have one AGM battery (100 AH), and 130-watts of solar for charging when dry camping. I do not charge my AGM from my truck. With the two trips I made, the one AGM worked just fine. I did not need to run the furnace, and if I need heat I use my Wave3. I really don't know how it will be during winter months with solar charging the battery.
Wayne
2004.5 Ram SLT LB 3500 DRW Quad Cab 4x4
1988 Bigfoot (C11.5) TC (1900# w/standard equip. per decal), 130 watts solar, 100 AH AGM, Polar Cub A/C, EU2000i Honda
Toad: 91 Zuke