Well I've had time to go through a number of different clipless pedals at work and home, taking crank arm face to center of cleat jaws dimensions. These measurements were done with a hand held vernier caliper and are likely within a mm or so or actual dimensions. I was impressed at how narrow the range turns out to be. Shimano SPDs of a few versions and vintages were all about 54mm. Crank bro. were about 53.5mm, as were the couple of Wellgos and Looks. Ritcheys were 52mm. On the road side I only had Looks of various versions and vintages which were all the same at 53mm. My Speedplay X2s are 53mm.

I haven't done this same exercise but with shoes. I suspect that the cleat mounting threaded points will have greater placement, WRT the actual foot, range. Also I suspect that for recessed SPD shoes (thing typical mountain shoes) the side to side adjustment ability, as limited by the shoe sole lugs, will have a range beyond that of the pedals. Lastly is the shoes "cant" or arch support. Both effect the foots placement and "feel" of how the legs work WRT the side to side motions during the pedal stroke. Andy.