After having used the mobicool on a few trips, I think its worth thinking through a few bits before buying it.
The major nagatives, addressable, are that its very badly insulated. You are almost certainly going to need to improve on that. Secondly the cooling coils are right at the base. Connected to a metal plate that does not come high enough. So yea, stuff at the bottom is going to freeze and go bad. And the stuff at the top is going to get warm and go bad. So you need to think through how you load it. And almost certainly going to want to use metal containers, sized properly to conduct the cold up ( or the heat down ). And then position your internal thermometer in a way to give you a realistic picture.
The it really does use, as they say, 5amp@12v when the compressor is running. Bigass battery need then for when you are parked up. Do the math.
Finally you do need to keep it well ventilated and out to the heat - it will only cool to a max of 23 to 28 deg below ambient. A problem somewhat addressed by better insulation and ventilation..... but being parked up at supermarket when we did some food ahopping and got lunch, with 32 Deg ambient, inside truck going to 40+...