When it comes to bearings, yes, there should be a gap in between the loose balls (not caged bearings). If you put so many balls in there that there is no gap, then they would ride on each other when the cone is tightened down and not spin freely at all. The pedal would almost feel stuck. Same for loose axle bearings, there is a gap that is supposed to be there. Too many bearings and you will have big problems.

Bearings are designed to break in/bed. They might feel tight at first but over use, will tend to loosen up. There should be no play when the cone is tightened down but it should not be so tight as not to somewhat freely spin.