Ah, found the section you where referring to about character!! Staff section in help section.
Drivers stats through the character is a bit harder to determine as it a bit of guess right now but I can try to explain what I think:
Morale, motivation & experience = speed
Ambition, motivation & experience = cornering
Ambition, intelligence & experience = wet weather
Professionalism & intelligence = technical ability
Intelligence & ambition = starts
Ambition, motivation & intelligence = overtaking & defending
Charisma & professionalism = contract length & terms
Hopefully I didn't miss anything since I wrote this from memory and on my phone!! Again this is my best guess as I don't have proof of all of these yet!!