Lets see if I can answer both sets of questions here: I truly believe that the RV interior is much cooler. It felt cold to my hands when I went on the roof a few days post application to remove the masking tape in 70 degree sunny weather. Before, in the same weather, I would have to put rags under my hands because of the roof heat. I don't use measured electricity, so I can't measure things that way, but I know my AC daily run time is much less than before. Read the thread I linked to again about prep and installation. This was applied outdoors at my RV site in So. Ca. Just fresh water pressure wash, mask, and 1 coat which dried in a few hours. I can't make much of a call about black streaks, but I can say that it makes the rainwater bead up like a good car wax job, so maybe the water wouldn't have time to grow the mold for the black streaks. I have read that you can apply some of the coating to new roof "wounds" as a sealant/repair, or use Eternabond. It will probably rip or tear if a tree limb is pulled through it, a it is like a silicone rubber thicker, slicker, membrane.
Here is a link to the Henrys webpage on their product:
https://henry.com/retail/white-roof-coatings/887-tropi-cool-100-silicone-white-roof-coating
