I played Mario Kart 8 and Mario Kart 8 Deluxe and when I noticed the names of the staff ghost profiles, they seem to be the same CPU Miis from Wii Sports Club and Wii Party U. Plus, I discovered their nationalities.
In MK8DX, there's two types of Traction: on road and off road. On road is the main road you race and and the value is 0.75 regardless of level. Off road is the stuff that slows you down. It has flags like DIRT, SAND and ICE. I've tried different combinations and I can't tell a difference...
Within Mario Kart 8, several courses utilised anti-gravity, which allows for racing on places that normally won't be drivable due to gravity, allowing for more uniquely-designed courses. The mechanic also has the perk in giving a slight boost when racers bump into each other or one of the posts...