I use the 1600 count boxes for nearly everything. The boxes for large stuff like exhibits I leave out the divider.
The cards are in a variety of holders. Most modern stuff is loose with better or problematic cards in penny sleeves. (Like modern die cut cards, or stuff like the GQ framed ones, or the one 59 Topps with sticky tape residue. )
Older stuff or really better cards get toploaders as well as the sleeve. Prety much all my prewar is in toploaders. Haven't found good holders for the unskinned old judges.
I also use some 3200 ct boxes for modern, but the newer ones won't fit toploaders so that will end eventually
Someday I'll build a cardfile type cabinet for a lot of that, anything better looking than the boxes.
The graded ones go in this table I made.
Steve B