Nomads sometimes speak of running loadsoff the panel; this means the loads do not affect the battery bank's state of charge because excess power is available.
Mobile solar power systems are not putting out full power all of the time, even in direct sunlight. This can happen when the batteries are charged and there are no loads on the system. When power is needed, the solar controller jumps into action and lets the panels make power again; it's almost instantaneous.
This means there can be a large gap between a) the power the system could make under full load in present conditions, and b) the power the system is actually making.
If you run your discretionary loads (charging devices, running heavy loads) when the system would otherwise be idle, you are effectively running the load off the panels. Battery state of charge is not affected at all.