How to calculate the proper layer height multiples?
that the NEMA17 motor would be using 400 Steps per mm in Z. configuration_adv.h tells that the microsteps on the Z-axis motor are 16.


Easy. There are 400 microsteps in a millimeter, and 16 microsteps in a full step. So, there are 400/16=25 full steps in a millimeter. So a full step is 1/25th of a millimeter, or 0.04&nbsp;mm. Your layer height should be a multiple of this.

As your leadscrew has a lead of 8&nbsp;mm (i.e., a full rotation will move the Z-axis by 8&nbsp;mm), a full step is either 8/200=0.04&nbsp;mm (for a 1.8 degree stepper) or 8/400=0.02&nbsp;mm (for a 0.9 degree stepper). So, apparently, you have a 1.8 degree stepper (and this is the most common type of stepper).