Are you referring to a sled topper? I have them on all my slide outs. I got them to keep the debris of the rooms, but I found out last week while camping in jackson, ca in about 98* heat that they also help provide some insulation. Even though our air ran most of the afternoon, I can say the the trailer was warm but not hot.
No, not a topper. An actual awning on the slide. I have seen them on a couple trailers. I find the awning is a bit small and too high to really do much.
If you want a power awning, it will take adding a bunch of wiring to make it work, and they are laminated slide walls, so you would have to run them inside somehow.