The short version is: For the most consistent layers I recommend that you use layer heights that are a multiple of 0.04mm between 0.08mm and 0.28mm.
Many variables affect print quality. This is just one thing that you can do to improve your prints, but it is easy to do if you know about it.
I’ll explain why in more detail in a moment, but the short reason is that the stepper motors “full step resolution” combined with the geometry of the screw in the linear module means that for every full step, the z height changes by 0.04mm. The controller and the steppers can do microstepping, but that involves trying to position the stepper motor somewhere between two steps by using dual voltages. The positioning of the motor at whole steps is stronger / more accurate / less minute variation.
Now for the breakdown. If you don’t care how this was calculated or where I got the information about this you can stop reading here.
Stepper motors have different poles (like a magnet, but in this case an electromagnet) where energizing each pair of poles, the motor turns to a new position. The Snapmaker uses steppers that are 1.8 degrees per step. This means there are 200 different positions that the motor can turn to by using whole steps. Microstepping applies voltage to two different poles (two positions) at the same which locates the motor somewhere between those two positions based on the relative voltage. This is pretty precise, but not as precise as the locations of the whole steps. If you use a layer height that ends up requiring microstepping, then one layer might be slightly higher or lower than another layer of the same height because of sight variations in the accuracy of the microstepping.
The Snapmaker screw inside the linear module travels 8mm for one whole revolution of the screw. So when the screw makes one full turn, the z height changes 8mm. The stepper motor has 360 degrees in one full turn with 1.8 degrees per step. This means there are 200 full steps in one complete turn off the motor and one complete turn of the screw. So, there are 200 steps in 8mm of travel. 8mm / 200 steps = 0.04mm per step.
The Snapmaker has a minimum layer height of 0.05mm. So, the next whole step size layer is 0.08mm. Other good layer heights are 0.12, 0.16, 0.20, 0.24, and 0.28mm.
I got the specifications for the stepper and screw geometry directly from Snapmaker. I learned about the relationship between the stepper motor whole steps and the linear travel from this YouTube video:
So, you can use any layer height you want between 0.05 and 0.3mm; I would highly recommend that you use and develop your settings profiles around multiples of 0.04mm layer heights.