Outside of the cable & adapter - don't you still need to purchase an actual wireless device? Totally confused here...
My understanding is you need to have a wireless device to place your phone on top of to "fast charge" it. Apple did a terrible job at explaining how to work this - especially not having the products "in the box" to make it work.
Fast charging and wireless charging are two different things in this case. If you charge an iPhone 8, 8 Plus or X via a lightning cable plugged into your phone, with a charger that supports fast charging (via USB PD) as Apple has implemented it, you get that benefit. If you charge wirelessly with a separate charging mat / puck / device, you charge at what I imagine is slower than standard speed.