TangoBlue
American Adventurist
Any of the panels you mention will *help*.
If you are only gone a few hours, and assuming your starting battery is in good shape and fully charged when you leave, you will be fine. I used to leave my fridge run all night off the starting battery -- but I never let it sit for more than 10 - 12 hours before restarting the Jeep, and of course the ambient temperature was lower at night than during the day, and the fridge had a low voltage cut off on it. On some trips, we even ran the fridge off of one of the cheap battery jump-start packs plugged into the cigarette lighter when using a car w/o a outlet that stays hot with the key turned off.
It helps to load the fridge with as much water as you can, and make sure it is cooled off to your set temperature before you park the truck and head out for the day.
That's been my experience too. I have my ARB mounted in the back of my truck and I'm either on the move or parked. I often go similar time lengths without impact to the battery. At night, I turn it off and have consistently noted a 4 to 10 degree increase so it maintains temperature very well. Bottom line... I think you'll be fine with a single battery with your described application. Give it a while and re-evaluate your needs after a few months of experience. I'll also share with you that dual batteries are in my near future.