It depends on what you desire to power. Easy way to get in the game would be get the suitcase and clip it on to what you have. That with a good battery will keep the lights
on and enough to run your 12v controls for appliances.
Next step up would be a good lithium battery and charger. 1/2 the weight
and twice the power storage or usable power.
One advantage of portable solar is you can park in the shade and put the suitcase out pointing at the sun. A 12v cigarette lighter plug type inside will power a small inverter big enough for an led tv or charging up a laptop....
Beyond that you probably get to the point you should review the old power distribution box and do an upgrade if your wanting more power.
If your thinking power an AC unit, run electric heat, any electric appliances then its a whole different game an a bunch of money for what in the end doesn't change your camping style much.
If your thinking mounting permanent panels to the top, continue to do research and be sure the top can handle it.