Some Lance units have fully decked roofs so you can walk on it to be able to reach all the places you need to caulk, others do not have that type of roof. You will need to check the specs on yours to see whether you can walk on it.
As to the exposed screws, those are along the rail and do not seem to be a problem. We found on our old trailer that the channels with the bubbled out vinyl cover (not sure what to call that) tends to come out of the channel over time. And the heat seemed to cause problems for that stuff. It was a bigger PITB than these exposed screws.
Ours did come with the solar panel. We had never thought about having one before but since it was there, we got it. I am so glad we do have it now that we have boon-docked for several more days at a time than we ever did before.