Not all power supplies like having external voltages present at their outputs. If it's not listed as supporting paralleling with other supplies, I'd be very wary of hooking it up to an RV 12V system with a battery and a solar charger/controller.
The output of the linked supply itself should be OK for powering RV circuits when used alone within its ratings. It's undoubtedly better filtered than many older converters, and probably not much different from most modern converters, being basically a fairly high-current switching power supply.