I mean obviously you're right; this is a land-yacht and not really meant for any real level of performance driving outside of quickly getting up to speed. I'm not racing this car nor going to be tracking it. The issue I was experiencing was that the vibrations would start within a few minutes of driving, even at lower speeds around 25mph-35mph, and get significantly worse and worse as time driving continued or speeds increased. There seemed to be no pattern to it. Within five minutes of driving the problems would start. The dealership over-inflated the tires, under-inflated the tires, put on different pads, different rotors, a different brake kit. Nobody knew what the heck was going on. I even did the "proper bedding in" with the service advisor and lead tech present in the car (they were driving not me) and it seemed to temporarily work until a few days later when the problem returned.
Here is my bottom line. The brakes (both pads and rotors) are on the cheaper side and not meant to be used on a vehicle with this level of horsepower and weight to haul around. Kia "tricked" the customers by having "Brembo" written on calipers but not having higher level brakes. I have driven cars my friends own which are just as heavy if not heavier than my Stinger (E63-AMG, Hellcat, Mustang GT, Camaro ZL1), and none of them have these vibration problems. The car should not be shaking when applying brakes at 70mph or after fifteen minutes of highway driving.
Mustang GT doesn't have this problem and that is a "Grand touring" car. Maserati GranTurismo is a "grand touring" vehicle and doesn't have this issue. The problem is Kia and not the drivers. Trust me on that.