I doubt it would make that much difference to me. Even if they knew my game and course better than me. It's still me hitting the shots and they can't do anything about that.
Assuming the caddie knows his stuff, probably several shots if I am playing for the first time at a strange course. Probably little difference at my home course or a course I know well, unless he is also a very good swing coach.
I'd go so far as to say they could take me round in 11/12 over. I play off 23. Why do I say that?
- I don't lose shots consistently over the course of a round. I tend to drop my shots on 4/5 disaster holes
- a caddy would keep me calm, keep me focused and help me play each shot as it comes
- They'd also help me play the percentage shot more often and,
- as they'd be looking after the bag and yardage all I'd have to think about would be execution
GM have done this before I think about e years ago. From memory the caddies walked the morning round learning technology players game then we're involved on the afternoon round and the highest handicap scored better.
It wasn't scientific but it was an interesting read...