I recommend that you think about the following:
First figure out how much power you use and need for the type and seasons of camping you will be doing. Remember to factor in consecutive days of low Sun, clouds, rain, etc. if appropriate to your type of use (boonie camping no shore power, occasional shore power, etc).
Size your Solar and battery storage needs to accommodate the power needs you have already figured out (above)
Think about roof weight and if you are going to need to replace your solar controller to accommodate the added solar panel(s)
Consider buying the largest single panel that will fit on your roof. It will be cheaper and lighter in total weight than any combination of two or more solar panels. Yes, I know you already have one panel but the additional cost of one large panel may not be much more than another smaller panel. I bought a 360 watt LG residential panel for $310 in May 2021. I did have to upgrade my solar controller with a new one to accommodate the new panel. I previously had two 100 W panels and the single new 360 W panel is less than the combined weight of the two 100 W panels. Only one set of wires too.
If you do decide to add a second panel to your existing system, assuming you are using industry standard MC4 connectors, you can buy a Y cable, to connect to panels to gether in serial or parallel, on Amazon.
I hope this information is helpful
Craig