i have questions about a 2021 Venture Sporttrek 332VBH

If your trailer came with an inverter not to be confused with a converter. Usually the 110bv outlets are labeled for power from your inverter if you have one. Sometimes it may just a 110v outlet by the bed for Cpap machine, it would run off your batteries. If your trailer doesn't have a inverter then it could cost some bucks running wires from a inverter to your power panel, that may take a expert on 12v and 110v wiring. Yes you can add another solar panel assuming you only have one panel. I think 2 would be the max, the bottle neck would be what your solar controller can handle, it your controller 10amps, 30amps or 50ams will determine how many more solar panels you can add. If you turn your battery disconnect switch off your solar panels by-passes the switch and will continue to charge your batteries. I would would leave the batteries in your trailer and turn off the connection and just let the solar panels top off your batteries everyday assuming you have sun shine almost everyday. I would check the battery voltage level for the 1st few weeks to make sure the solar panels are keeping the batteries charge. The wiring is already on the roof, just mount another solar panel and plug right into the eating wire.