Questions about print quality and electronics..

Hello! This is my first post on the forum as I begin the learning process of 3D printing and the mechanics behind it before buying my first machine.

I currently own a CNC and want to also do some 3D printing so I understand the basics of how things work but I'm curious about how to determine the print quality/layer thickness/electronics?

I'll probably buy a kit my first time out, maybe even the Prusa i3 MK2, I've also noticed there a lot of knock off's with all different features mostly due to the open source.

So here are a few starting questions for me...

1) Layer thickness, what determines how thick a layer is? The thinner the layer the less noticeable I assume... what gets one printer to 50um and another to 100um, um I think is the correct measurement?

2) Electronics control board and I'm guessing a driver board, what is the standard? are they all based on the Arduino? Is the ATmega2560 and RAMPS 1.4 kind of the industry standard? Is that the combination that they call the "RAMPS"?

3) Print quality, is this the same as layer thickness or are they different and what's the determining factor there?

Any insight you can provide would greatly be appreciated as I try to steer my way thorough the new terminology.

Thanks.

Ampapa,