I have a Waeco Combicool 60, 12v, 240v, and Gas. Its big and I can make ice..
The fridge is getting on a bit, (2006) the 12v is a battery killer so I don't use it much. If I do, I will first fill the fridge with beer and get it properly chilled on 240V, then keep it cold on 12V while driving, then use gas or hookup while camping. Mine works well on Gas.
I have a the basic split charge from JK, its not intelligent just a simple relay actioned by the ignition, it keeps the battery topped up. From the leisure battery I have run cables to under the bed and have a fuse and distribution to an Amp, I also have a capacitor before the amp to smooth out peak bass power drain...
I run the Stereo from the leisure battery too, I recently added a timer relay (from 12v world) powered by the leisure battery triggered by the ignition. The timer stays on for two hours after the ignition is turned off so I can run the Stereo. I had an issue with the Stereo where it kept on draining the leisure battery when stood for a long time and I did not want a separate switch.
In the glovebox I added a USB charger with a digital volt meter, then added a double pole switch so I can see the voltage of the main and leisure battery, gives me confidence everything is charging while the engine is running.
For hookup I run a cable and post it through the side window
Crude but works! I would like to hardwire the 240v, perhaps introduce a battery charger / maintainer for leisure and main. The caravan folks have some options but they are not cheap or small.. I played with Solar for a bit, but at the time panels did not produce much and unless you are off grid for more than two weeks its not really worth the hassle, but as a geek I had fun!