@
theCROM
how often will you be needing to run it overnight?
The stock size battery should have enough capacity to run your fridge overnight on an occasional camping trip, the issue is that the stock type battery doesn't like being discharged that deep so everytime you do it you are shortening the life of your battery.
My stock battery lasted about 6 months running my fridge 24/7 with some maintenance charging before i started to see reduced performance. so if you are just doing an occasional camping trip your stock type battery is fine, just maybe carry a jump pack for security
the next best step is to replace your starting battery with an AGM type, and when doing this you can also increase the capacity with a larger battery. you will need a voltage booster to charge correctly, but the AGM battery isn't as negatively impacted when you discharge it.
your use case doesn't sound to me like you need dual batteries, unless you just have the money and want the security; what i would do in your case is just carry a reliable jump pack if this was just an occasional thing or upgrade to an AGM if more common
yes run a dedicated 12v outlet, the stock wiring is small and causes some fridges to shutoff from voltage drop
also, don't get a goal zero, there are better options for less money