Can't go wrong with redarc. Victron makes great systems but its generally more parts to get everything going. But lets listen to the other posters here for a second and go back to
simple. I think these days most people can actually get by with the "
solar generator" (i hate that name) style boxes that have lithium batteries, dcdc chargers, solar mppt, inverter all in one. They are simple, plug and play and if all you really use for electrical loads is a fridge and you drive quite a bit, then they are enough. They generally have the downside that they charge slower than purpose built systems, but they do have a lot of capacity compared to an AGM/lead acid setup. (my dual AGM setup only actually added less than 50 ah of usable power and it killed batteries constantly even with constant shore power charging). Not to mention the voltage drops dealing with lead acid/agm just sucked. Any large load like a rv water pump or my air compressor would drag voltage down enough to reboot my HAM radio sometimes.... I run a lot of stuff so lead acid had to go. Not enough capacity given the weight and system complexity and tie in to vehicle charging systems. And constantly killing batteries with real world use. (which is why im generally not a fan of dual agm battery setups. Having a Redarc dcdc between two AGM is way battery than using solenoid or simple bridged systems that rely solely on the alternator directly charging them.)
So think about that simple option before going dual battery because you really do get more capacity and all those components in one go. Cost/value wise I don't think its possible to beat that.
Now if you have heavy power requirements, want to run lots of loads, electric heat, etc then I think a purpose built rv-like/camper-van system with discrete components makes sense. My setup is fun to show off, but I always fully admit upfront that its costly, excessive and just generally cuckoo... but I love it... haha.
For me the holy grail is in-cab LiFePO4 house batteries (2x Renogy 170ah LiFePO4) and components. wagantech 1kw Inverter, victron 25amp shore power charger, victron mppt for solar blanket (which i don't really use anymore), redarc DCDC 50 amp for a majority of charging needs, plus some nice victron bus bars (lynx power in) and victron smart shunt to manage monitoring. It leaves the vehicle start battery largely alone, isolated when the alternator isn't running which keeps it healthy.