Bit late to the dance on this thread, but wanted to offer our experience. Though we’ve used a variety of dual-battery options and solar generators over the years in our old RVs and in friends’ rigs, what we ultimately landed on for our truck was a hybrid solar generator / dual battery setup. We have a detailed explanation of the exact setup here (towards the bottom)
But essentially: we use an old 1100watt Inergy Kodiak lithium solar generator, that has a 12v DC charge rate of 240 watts through the car charger, this was double the rate of the Goal Zero options at the time (Goal Zero did briefly offer an adapter called the Yeti Link Car Charger that allowed for even faster charging, but they’ve discontinued it, at least for now).
This faster charging rate allows us to fully charge the generator off the truck’s DC in about 3.5 hours of drive time, and we can supplement with solar as needed (though on our last one month trip we didn’t even bring the panel, and never needed it). We’ve run our fridge, lights, (a vent fan before we got the GFC), and charged two laptops and two cell phones daily for 4-6 weeks at a time with this setup over the last couple years.
Unfortunately, Inergy discontinued the Kodiak awhile back - but their new model the Flex is due out soon and looks to be an even better solution…time will tell.
What you need will ultimately boil down to your specific personal power needs, cost, and how comfortable you are with the complexity of install (or paying someone who is) - we’ve found solar generators to be a better long-term investment overall because of their portability, versatility, simplicity, and weight-savings compared to traditional dual battery setups using AGMs or lead-acid.
**Know that we’re not sponsored by Inergy (or anyone for that matter), just super stoked on their product (they’re based in Pocatello, ID too, which is cool because 'Merica), and while there’s a lot of hype on the Goal Zero and Jackery stuff - like to point out there are alternatives.
Hope this helps.