A very upright backswing will have the leading elbow pointing essentially straight down during the first part of the downswing. The inner cup of the leading elbow on the other side of the leading elbow will point straight up during the first part of the backswing.

A medium upright backswing will have the leading elbow pointing much more downwards than upwards out to the target line.

A flat backswing will have the leading elbow pointing out, specially the leading forearm pointing much out toward and above the ball and the target line, because of the extra twisting and rolling of the leading arm during the flat backswing.

Keeping the leading elbow, and the bottom edge of the leading forearm pointing down, and the inner cup of the leading elbow pointing up during the first part of the downswing helps to start an upright back swing.

Minimizing any rolling and twisting of the leading arm during the backswing simplifies the downswing for more accurate and consistent downswings. This is the one-piece takeaway. This is called the square-to-square swing.

Cupping the leading wrist at the top of the backswing can make things more complicated, according to some Youtube clip. It is simpler to keep the leading wrist flat at the top of the backswing. Hogan cupped the leading wrist at the top of the backswing. His movie clips showed he then flattened the leading wrist at the start of the downswing to a slightly bowed leading wrist position at the start of the downswing. These days the flat leading wrist at the top of the backswing is considered the ideal, as the flat leading wrist should be flat at the moment of impact during the downswing.

For me, my straight shots come when I relax and swing at maybe 75% of my power, full swing, but just kind of care free and easy. As I put more in the fairway I get more amped, until I send one into the woods