Whitewolf, I can't give you before and after temps. We have slide toppers on our current trailer and I can say they are worth it - and yes, they flap in the wind and they can fill up with water and you want to be careful with ice. Choose a light color for your awnings, white tends to reflect the heat better. If you are in a seasonal site and don't move much from location to location you could shove lengths of blue Dow Styrofoam between the slide roof and the awning. I don't think storing perishable food in the upper cupboards is a good idea in any RV, even in our house with kitchen cupboards on the south side and R20 insulation it gets to warm.
As a side note, our last trailer had a so called Arizona Room (4 skylights over the dining room slide, with full screen like awning going over top and pleated blinds underneath) - the worst thing ever.
2013 RAM 3500 Longhorn Dually, Andersen Ultimate 5th Wheel Hitch,2014 Trilogy 3650 RL, 8000# axles, disk brakes, I.S., 960 Watt Solar