The upright growth should be signifcantly more than that of the lateral growth. If I were using them for this, I would place them closer to 10 ft apart. It is unlikely that they will grow together near the ground as the habit is usually quite vase shaped. Therefore I would plant some type of evergreen shrub between them to fill that void.

I don't know that I would call there growth very leggy. If anything, I would call them twiggy. There are generally many small branches packed closely together all the way up. They usually do form a fairly dense mass of branches, and should make a descent screen.