When you are rotating the barrel to hit the ball, should the barrel be vertical or horizontal at the point of contact? Like this \ or like this --?
The angle of the bat at impact is not as important as the angle of the body at impact. Check out this post on my hitting blog for more of my thoughts on where the bat and body should be at impact. Stay On The Right Path | Hitting With Torque
The quick answer here is the bat should be relatively level at impact. If the hitter has close to full extension at impact, the bat will meet the ball on a level plane. However, the angle of the shoulders at impact will ensure the bat head begins to rise gradually after impact in order to drive the ball.