IMO it is irrelevant. All the Bob's drive like noobs until about level 15/20.
Then they know how to drive and it's just down to the right car really.
Just level up as quick as possible (remote races?) and then set him to work. The difference as he reaches the 'good' threshold is so noticeable its funny. One race he's all over the shop. Next he is scagging the AI left right and centre. Have patience! 👍