I put the Carefree one you have pictured on both of my 40' 5ers. Both awnings sagged when they were delivered. Most people think it's just natural, but a dealer tech told me a while ago that any awning over 16 feet needs an awning cradle. Most of the sagging could be stopped if the factory would install these prior to leaving the factory. Once they are transported across country, the sagging had already happened due to the length and weight of the awning when rolled up, and the continuous bouncing of the camper in transit.
And YES they work with power awnings as both of mine are power. Just remember to rivet them into place with aluminum or stainless rivets, or bolt them in with stainless bolts to prevent rust stripes down the side of your rig!