The reason that -- at least on the Sauber -- the speed is displayed so large is that it's the number that's changing the most rapidly. It isn't a primary piece of information, but when the car is accelerating away from a corner, the driver needs to be able to discern acceleration by way of more than just the seat of his or her pants. With the immense amount of torque available this year, being able to optimize that acceleration out of a corner is absolutely paramount.

The "marks to hit for straightaways or (...)" are visual indicators on the sides of the track, showing the distance to the corner. Part of what makes these drivers the best in the world are that they're able to hit -- mostly -- the exact same braking spot coming from 300kph down to 60kph lap after lap after lap, without a computer telling them when to brake.

Coincidentally, that row of LEDs on the top of the wheel is supposed to tell drivers when to shift, but teams found out a long time ago that the visual indicator wasn't being processed fast enough by the drivers' brains, so now drivers get a little beep in their ear when they're supposed to up/downshift.