My Ineos has a single battery and I recommend a fridge to avoid the hassle of loading/draining bags of ice. I purchased a cheap 45 litre fridge freezer which in my opinion is as cheap as one of the more expensive coolers. Most of the fridge/freezers are all made in China anyway, all rebranded. I can buy things frozen from the supermarket and not worry about it melting.
To keep things charged up, I’m using a Bluetti charger 1 alternator charger with a Bluetti power station and tops up whilsts driving to destination's super fast, much faster than a 12v plug. Whilst camping (stationary), I then keep it topped up using foldable 200w solar panels. I use the car 12v to power the fridge whilst driving and then plug the fridge into the power station whilst camping.
It’s a cheap and modular way with many power outlet options.