Toolboxes only come in one size, it seems - too small! When I built my toobox-to-last-forever 25 years ago, I thought I owned all the woodworking tools I was ever going to need, but just in case, I left plenty of room for future expansion. It wasn't many years before it was overflowing.
I went through the motions of setting up tools & measuring what they needed & trying to work it all out so I could make Studley-like use of the space, but it all got too complicated so I just went for lots of shallow drawers and shelves for larger tools like planes. The drawers range from about 25mm high (that's the usable depth) to about 100mm, which covers a wide range of hand tools like marking gauges, chisels, hammers, etc. etc. I made shelves that press-fit into the upper section for planes & that proved to be a good move as I have remodelled the plane shelves twice since I made the toolbox.
Also, I used scraps to make press-in fittings in the drawers - again, it makes life easier when the inevitable reshuffles occur:
My drawers are about 400mm deep (long), which I find comfortable - not so deep that stuff gets lost at the back, but deep enough they don't fall out easily if opened a bit carelessly. Mine accommodate long paring chisels comfortably:
Making places for each tool is a bit of a task but it makes it very easy to see that all the chickens have come home to roost at the end of the day, especially small things. More than once I've noticed a spare space when packing up & found the culprit hiding in a pile of shavings & in danger of being swept up & binned!
Everyone has a different set of tools to house, and different ideas about what they want, so the best idea is to look at as many other toolboxes as you can & snaffle the ideas that appeal most to you. My overall plan when building the above was to have every tool easily accessible so that I didn't have to shuffle anything about to get whatever it is I need. To that end I succeeded pretty well (there are a couple of much-less-frequently used tools that need a bit of shuffling to access, but only a few).
So I guess my advice is to make sure you have more room than you think you need & fit it out so that at least a substantial part can be remodelled reasonably easily.....
Cheers,
Ian