For me personally, I'll 'precool' the fridge by having the camper plugged into shore power and using the AC option 1-2 days before leaving on a trip.
Then I'll transfer precooled items from my house fridge/freezer to the campers fridge/freezer. I'll usually SHUT OFF the campers fridge/freezer before pulling out of my driveway.
While I live in Oregon and travel mostly in Oregon/Washington and the temperatures generally don't get higher than the 90's, I've found that the campers fridge/freezer will keep my items just fine (no matter what time of the year it is) during the 1-4 hours it takes to reach where I'm going.
When I reach my destination and start setting up, the campers fridge/freezer will get turned back on set to AC (if available) and propane if AC is not available. I see/find no need for the 'DC' mode/setting at all.
Obviously YMMV,
- Mark0.