Electrics is one thing I'm really not sure about.
It's not the easiest thing to understand and varies from person to person and trip to trip, but you'll get the idea once you test it all out. I'll just mention a few things as food for thought.
To work out your ELEC system needs you need to understand:
- 12V consumers. To know average Ah consumption and also the peak Amps to allow for. An inline power meter is very handy to help understand
- Charge methods available (mains power, tow car, solar)
- Anticipated duration off grid.
If the CT battery charges while driving you can be pretty sure of a full change when you arrive at a campsite, and I guess a full charge will give you ~2 days without any top up from solar or getting too low on your battery. Hopefully solar tops up, but if not you can run the car.
If you're planning on a lot of off grid camping over coming years I'd suggest biting the bullet and upgrade now if time and $$ permit. It's probably not necessary for this trip, but it might give you a bit more flexibility/options and eliminate the need for any powered sites.
FYI I reckon the minimum spend for upgrading to 100Ah lithium is around $1K DIY. You'll probably need a new chargers or two that supports lithium. Doing so will give you about double the useable capacity and save ~15kg weight.
An alternative to upgrading the CT system is to supplement it with a separate standalone power station. eg.
https://www.anacondastores.com/camping-hiking/power-cooling/generators/ecoflow-river-600-max-power-station-576wh48ah/BP90173897-black
Could be hand if you head off on a day trip with fridge in the boot and and want to keep it powered.