I work for a Volkswagen dealership and the manufacturer trains us "crimp only, no solder". I understand two concerns - 1) that soldering is a learned skill and quality can vary. 2) the edge of the solder joint can be a brittle break point.
As such we have ratchet crimp tools and most factory joints are crimped or sonic welded. Also all connectors are heat sealed and/or shrink wrapped. Here is a poor picture of a training aid in class.
My understanding on conductor is solid is cheaper to make and is fine in a house when it won't need to move, much. Stranded allows flexibility and limits damage due to flex and bending. Finer strands (ie welding cable) allow large current flow while still allowing repeated bending and easy movement.
Insulation is another where house is pretty well protected from the elements and has low requirements. Automotive on the other hand varies from interior to exterior and resistance to temperature (freezing and hot exhaust) and chemicals.
A good general purpose spool of automotive wiring will work in your, well sealed, camper. But if you have to make runs that exit the camper (ie lights
on tongue, etc) then a higher grade insulation and possibly tinned conductor is advised.
This is all 12v systems. A 120v system has similar recommendations for conductor and insulation, but obviously with higher voltage potential more caution is advised.
A side note, I finished a Hybrid vehicle training class. Lower voltage DC will kill you faster than the higher voltage AC. Jason