Determining the draw length you should shoot is afirly complicated if you do it right. Best way is to measure your wingspan and then divide this by 2.5. This gives you a starting point and by shooting and tweaking you adjust the bow till it fits you. This is not a matter of a inch here, an inch there--nor even in half inch increments. It gets down to the last 1/8". When you have the bow adjusted till you are rock solid on the target aiming becomes very easy.

The draw length of the bow is determined according to
AMO" standards. That being, when a bow is fully drawn, it's the measurement from the nocking point on the string to the deepest part of the grip (True Draw)---then add 1 3/4". This may end up being to the far side of the riser, but often not. Assume that your bow has a True Draw of 26 5/8". Then you add 1 3/4" and the AMO draw length, which is what the bow is marked for, should be 28 3/8". Of course bows aren't marked this way. They usually come in even 1" increments such as 28" or 29", which is their AMO draw length. Their True Draw would measure 26 1/4" and 27 1/4" respectively. Confusing isn't it. Just compute everything to AMO specs.

The length of the arrow, as you describe has no relation to draw length. You may have a 28" draw, but depending on where the rest is located in relation to the riser can determine what arrow length you choose to shoot. As long as the arrow is not drawn off the rest when you draw the bow it is long enough. Longer doesn't hurt a thing. In other words I have a 27" draw. I shoot a 27" arrow even though they extend past the rest about 1 1/2"---nothing to worry about.