I had a 2006 Lance 845 with a 3 way frig.
I would always plug the camper in to AC power and run frig for 24 hours before leaving on a trip to get it cold. Once I was on the road, I ran on DC to
maintain the temperature. Why use propane if you don't have to! It never gave me any problems, kept the frig at the desired temp and the current draw on your truck batteries while driving is negligible.
If you start-out with a warm refrigerator, it would probably take a week for it to ever get cool on DC alone, if at all.
My 2008 Arctic Fox has a 2 way frig. I wish it were a 3 way like my Lance. Not sure why 2 ways are used some times and 3 ways on other occasions, unless the 2 way is cheaper or maybe it gives better service since it is less complicated.
Thanks much