Like others, we plug the van in the day before departure and set the fridge on 110 and it cools overnight. (If it's hot outside, we also run the A/C to cool down the van.) Next day, fill it up with frozen and already-cold food. Stays cold enough after that on any setting.
Driving down the road, we run it on 12 volt. When we stop for a few hours of sightseeing or stay in campgrounds without electric, we switch to propane.
After a month in the desert Southwest when the propane option wasn't working ...and we had to use a cooler and mess with melting ice...I love the propane 3-way. Even if we had solar and extra battery power, I'd be glad to have it available.