Been running an ARB 50 qt for a few years and like the size for both extended adventures and shorter getaways. It's usually just me, in which case I often stock it with a 12pack and/or water bottles as well as just bought frozen items and other groceries. I like buying a lot of fresh veggies and proteins too, and I fish a lot, so having a 50 is great. When I have company camping for a day or two, easy to have enough room in the fridge. Even alone, though, I sometimes wish I had more fridge space for longer trips.
Power draw is minimum on these--and most good 12v fridge/freezers.
Here's a good page on typical ARB draw and battery sizes that may be of help in choosing what's right for you, even if not an ARB:
The ARB Fridge-Freezer and Battery Life - What You Need To Know.
What's really more important in keeping even a minimum power draw down, no matter which size or brand, is to keep your fridge full. It will cycle less, won't work as hard, and will use less power if everything in there is cold and it's not trying to keep air space cold, too.
I keep a small soft-sided thermal cooler to the side with a bunch of soft freezer packs and several of those small hard blue freezer blocks. I tuck them in the nooks and crannies of the just stocked fridge, and when I take something out for a meal or drink, I replace it with another freezer pack from the soft cooler.
Having that small soft cooler with a bunch of freezer bags is often a good place to keep fresh fruit when in the heat, too. I try to keep my fridge out of direct sun in summer, as well. Also has a insulated jacket, which some think is frivolous, though I've found really helpful.
Also, keep the fridge vents free from being blocked. I see fridges all the time stuffed into a space just wide enough to hold them. Then the owner wonders why his fridge is working so hard. They need a little air around the vents to dissipate the heat they've removed.
Another thing I've found really helpful is to be smart about packing your fridge, with most often used items more accessible and in their own place (like a quart of milk that always slides in and out of the same spot) and condiments etc in small square ziploc containers on the back shelf where it doesn't get as cold (at least in my fridge). Then I lay a thin thermal layer over the top of everything; it's sort of a reflective bubble wrap meant for freezers and coolers. I cut it the same size as my fridge's opening. Then, when I want anything out of the cooler, I fold back whichever half lets me get to what I want, keeping the other half covered.
Plug it into 110 before heading out to pre-chill it if it hasn't been on 24/7. If you leave it on all the time, even when home, keep it full of gallon jugs of water and freezer packs if not using it to store food and drink.
Working it like this, I can keep my stuff cold in my fridge even without being powered for a day or so, even in the desert.
Good luck with finding one that's just right for your setup!
.