About 2 years ago I built a compact stand-a-lone system to run an engel 35 as a freezer and couple 12v sockets (charge devices, run fans, etc). It can run the freezer 4 days without needing a charge. With three 115 watt solar panels I never needed external power last summer. Basically if I get half a day of sun every 4 days the system sustains itself.
Components include, 100 ah lithium battery, victron solar controller, victron battery monitor and shunt, Bluesea distribution panel, three breakers, a battery fuse, a plug in victron 15amp smart battery charger (haven’t needed this yet) and 3 solar panels.
I contemplated an all in one unit like the jackery. At the time their solar charging was very limited and slow. They have improved a lot since then. I do still like individual components over an all in one because you can spread the components out so can be out of the way more that a single big box.
If doing it today I would look at SOK or Ampere Time batteries instead of battleborn. 1/2 to 1/3 the price. I used victron which is more expensive than other brand but their solar controller is very compact for space saving.
I’m enjoying your camper box build on the gladiator. Hope this helps in your decision.