I've driven something like 60,000 off-road miles since I bought my first truck in 2005. For overlanding, all you really need is a one big, high quality battery. The Odyssey PC2150 series are great batteries. Not cheap, but fantastic. It's very difficult to kill one.
Also, you'd be surprised how little energy you actually use out there. A quality fridge-freezer like an Engel or ARB can be run for days before it will discharge the battery in a parked truck enough to not turn the starter. This scenario pretty much never happens, so get a good battery, a good fridge, and you'll be fine.
Out of curiosity how far off grid do you go in your truck. That is, how far by distance and time are you away from the grid and stores? I know little about this stuff but am interested and would appreciate any helpful resources or videos you know of for a newbie. I’m interested from an overlanding / camping perspective but also a bug out vehicle perspective.
There's only so far you can get off-grid in the USA. The most remote is probably the Owyhee Desert, which is centered around the intersection of Oregon, Nevada, and Idaho. Out there, you can easily go 80-100 miles off pavement, sometimes further.
Another similarly remote place is the Arizona Strip, the portion of the state that lies north of the Grand Canyon. You access it from Utah and it's 95 miles from the outskirts of Hurricane, UT to SB Point, above the canyon.
Generally, we stay out for about a week and half and come in to town every 2-3 days, mostly for gas. We run Engel fridge/freezers, which give you essentially unlimited cold drinks and the only real limitation is space for fresh food.
It is an interesting feeling when you are truly bugging out or off the grid, almost a primal kind of thing, because instances where self reliance is the only thing left is becoming less and less of an occurrence. If you ever go camping in the wilderness by yourself and set in for the night alone, you probably know the feeling!
Also, you'd be surprised how little energy you actually use out there. A quality fridge-freezer like an Engel or ARB can be run for days before it will discharge the battery in a parked truck enough to not turn the starter. This scenario pretty much never happens, so get a good battery, a good fridge, and you'll be fine.