Best way is to read the data plate for the fridge in question, current draw varies greatly between fridges.
You want to find the one that lists the least amperage on the data plate.
The more bells and whistles the more the amperage on the data plate.
You are looking for one that is 1.1A- 1.2A for the compressor, and defrost mode of about 2.5A. Some fridges use a electric heater around the doors to reduce moisture build up, these types often will have a current draw of about 6A when running and those are the ones to avoid.
The lower Amp draw fridges tend to use a few loops of tubing around the door to reduce the moisture and thus have a much lower data plate amperage. These are what you want.
As far as run time, I have a 10 cu ft Haier brand (looks like Magic Chef, GE and a few other brands which can be found at Home Depot or possibly Lowes).
Typically mine runs 25%-35% from 70F to 90F per hr.
The data plate on mine listed 1.1A draw but my actual measured draw was .9A or about 108W at 120V.
Mine has a auto defrost which kicks in every 10hrs of compressor run time, in my case I added a switch which allows me to disable the defrost cycle for traveling. You may want to plan in the defrost cycle into your numbers.
My setup we have only one pair of 6V GC batts, gives us enough capacity to go about 24hrs before charging. But keep in mind I am using a Tripplite PV1250 inverter which has a power save feature. The power save feature turns off the output of the inverter when no AC load is detected. This feature saves me about 20Ahr-24Ahr of battery per 24hrs.
Since you have two pairs of GC batts and 300W of solar you should find that the fridge isn't going to drastically change your camping much other than perhaps running the gen a bit more.
Keeping in mind, removing the RV fridge you are eliminating wasted power from the 12V control board and gas valve in the RV fridge.
