Generally, keep this low ( 2-3 ) to maximize downforce, but raise it for bumpy tracks or if you're frequently bottoming out on kerbs.
Manual gearing is significantly faster, allowing you to use engine braking and ensure you're in the optimal gear for every exit. f1 2010 setup
Aerodynamics are your primary tool for managing high-speed stability and top speed. Generally, keep this low ( 2-3 ) to