Ah yes -- the simple question that can't be answered!
I have a fairly old Lowepro Micro Trekker that holds most of my Canon FD gear (an A-1 and 3 or 4 FD lenses plus some miscellany). I also have a more recent Lowepro Computrekker that can contain most of my Bronica SQ-A gear -- only problem is I could probably not carry it more than 200 yards full! In both cases, I use those backpacks mostly for storage. In use I tend toward a not necessarily photo specific shoulder bag or fanny pack -- or just a strap around my neck -- depending on what I view as the needs for a specific day/project. I sometimes use one of a couple of non-photo shoulder bags ("man bags") to one of which I've added a bit of padding. In the dusty archives is an assortment of pretty conventional "gadget" bags, some going back about 40 years.. And yes friends, I still find myself eyeballing new bags now and again.
I have a Tamron pouch, part of a modular series, that can hang on a regular belt. It will pretty much fit my Ercona II 6x9 folder (and little else). It can alternatively fit my Perkeo II 6x6 folder plus a Gossen Digisix, filter or two, and two or three rolls of film.
I also have a Think Tank "Urban Disguise 30" -- a nice non-camera-obvious bag. That can carry a fair amount of stuff, but getting larger things in and out can be a bit tedious because it has a zippered slot, not a liftable lid. I also own a Think Tank "Digital Holster 20" which I sometimes use to carry digits, but it also fits other SLRs (and is pretty obviously camera related).
And then there's a 4x5 press camera, a 4x5 pinhole camera and an 8x10 pinhole camera -- those I try to find subjects near where I can park the car!
So basically, in my opinion, there's no answer!