i just watched mine. my queen was a super layer and went right to work filling frames with eggs. we also had a really good early bloom on the fruit trees, so they had plenty to bring in. i added my 2nd deep at 4 weeks and a 3rd about 6 weeks after. then 2 honey supers. that was much more than i expected from 1 3lb package.
you'll kind of get a feel for it, and i think most people will tell you that more room is better than not enough.
i'll let others talk about going with all one size box. looks like a good idea but i got a good deal on deeps and frames, so i'll stick to those for brood boxes.