What are these three options on the kart selection screen?
Looking at this screenshot for reference:
Source
From left to right they are:
- Smart Steering
- Tilt Controls
- Auto-acceleration
They toggle these options either on or off.
What is smart steering and auto-acceleration? As one source words it:
The two options are pretty self explanatory, but they allow you to either have the game auto steer or leave the gas pedal down. It lowers the skill ceiling for new players by letting them focus more on learning the courses or using items without having to fiddle with anything else. It can definitely automate the experience a bit, but it hardly ruins it for "expert" players.
It looks like for expert players, you may want to disable these. But for people with disabilities such as the source discusses, or if you are a new player, they make the game much more playable.
Short answer: (From left to right)
-
Smart Steering, Pretty much you can't fall off the edge or run into some obstacles. You can although jump off the edge, like with a ramp.
-
Tilt Controls, steer your kart with tilt controls
-
Auto-Acceleration, you can move your kart without pressing any buttons. You can slow it down or stop it by braking.