Mine are pretty tight. I don't really have stacks next to each other, but between cabinets (one door back to the next door back) looks like about 1/4 in, maybe less? The drawers are all very tight top to bottom, definitely less than 1/4 in, more like 1/8 or less in most places. They gaps look wider in pictures from the front because of the edge profile, but looking from the side not much space at all.

Thickness of a nickel should be just about perfect...have been using that trick for years, much easier then trying to measure 2MM (or a light 3/32") via tape measure!

There is no real standard that I know of, the higher end European brands are pretty much right at 2MM...American brands tend to be closer to 1/8"...of course that is based on my personal experience

I would suggest keeping a slightly larger gap between the bottom of the counter and the top of any doors/drawer fronts

I have 1/8" in each direction. It looks like 1/4" from the front because of the bevel at the face of the drawers, but pull the drawers out and measure and it's 1/8" on the nose.

I'm used to 1/16" per edge making 1/8 between doors, drawers both side to side and top to bottom. Bottom edges flush, top edges 1/4.
Nickel sounds good if making em.

We're in the process of getting "adjusted" now that cabinets are installed...we are about 1/8". Truth be told, that narrow of a gap is making me a little nervous...I keep thinking that they are going to hit one another.