Wireless chargning on iPhone X and 8/8+
I am mightily confused about wireless charging options for iPhone X and 8/8+. With the myriads of chargers available out there, I am not sure how to identify those that can “fast charge” an iPhone at 7.5W. I see numbers of chargers promoting themselves as 5W-10W compatible. However I read that not all of them can charge an iPhone (equipped with iOS11.2 of course) at 7.5W. Is this true? Or is it just urban legend being spread by Apple marketing folks to steer iPhone owners to purchase their own offerings and those of their partners?