As to the big ones...every sheltie I have owned, with the exception of one little blue lass, was well oversize for the breed standard. Both my current blues, Faelee and Sketch, top the scales at 36 and 37 pounds with not one single scrap of fat on either one of them. I don't have a wicket for percise measurement, but both are probably about 20" at the withers.
Several years ago, when the AOL sheltie board was still active, someone came on the board and posted how she hated shelties that were big...she referred to them as "big fakes" and said she would never want to own one. It became a joke for all of us on the board who had big ones and from then on we lovingly referred to our biggies as "Big Fakes"...a title they held/hold with great honor.
Trini and my gang