What effects does strong right hand grip have on takeaway and top of swing?

[StefanUrkel]

I know it causes you to have a cupped wrist, but can it cause across the line?

[saevel25]

I know it causes you to have a cupped wrist, but can it cause across the line?

Not really. You have someone like Dustin Johnson who has a bowed left wrist with a strong grip. A strong grip doesn't necessarily produce a cupped position at the top.

If Dustin had more of a cup then the shaft would probably be pointing more towards the right.

Being across the line at the top of the backswing has more to do with turn rates and how your arms move. If you take the club too far inside and around you it can point the club across the line at the top. You can also overswing, see Bubba Watson or Phil. If they stopped at parallel they might not be across the line.  The position at the top has more to do with the overall swing and less to do with the grip.

Here's a pretty good thread on gripping the club