Hello, Folks, my first post here:
I am a modelmaker with decades of experience in manual techniques who now wants to make the leap to 3D printing for a model I've been contracted to make for the New York State Bureau of Historic Sites. I have 16 years of experience in 3D modeling but am doing my first .stl files. At this point I have two fundamental questions that I need advice on.

First - overhangs. I understand the premise and am trying to divide my models to minimize overhangs, but here't the question - let's say I have a vertical surface with a shallow horizontal overhang. I'm doing architectural models - so imagine a groove between two siding boards, or a groove between stones, or the top of a door or window frame. Let's say these features are only a half a millimeter deep - possibly less. Is there some maximum/minimum depth below which overhangs will print properly? If so, what values are safe? Does it depend upon print resolution?

Second - is there a need to model in units of the print resolution - in all three axes? For example, let's say I've got a printer with a 100 micron z resolution. I model a feature that's 197 microns tall - or 178, or 220, you get the picture. What happens? Does the slicing software average things out to the printer's resolution, or will the print fail?

Thanks for whatever feedback you can give me!