Champion Jockey: G1 Jockey & Gallop Racer

How do I use "Horse style" grades during a normal race. I see the 4 grade levels ( some colored dark green or light). I am not sure how to use that info during the race.

Also, can someone explain the bit control. When do you guys increase or decrease it ?

Right now I am playing the game on custom controls ( with many things done auto) while I figure things out.