whay would be considered the best combination of height weight and reach for the upperweight classes?
I don't think there is an ideal height or reach for any weight class but generally speaking certain body types lend themselves to certain styles of boxing.
body type is better suited to style rather than weight class. tall and rangy - outfighter short and stocky - infighter etc etc you will always get the same builds repeating they will just be scaled versions in different weight classes.