Not quite sure what this has to do with the Ramps board .....
1) Your bed needs to be level or you need to use auto leveling
2) Since you are (apparently) using a max end stop rather than a min, things that impact the travel distance need to be well controlled.
3) With your nozzle, a layer height in the 0.2 mm vicinity is possible.
4) Holding your zero to 10% of the layer height is a good idea, that gets you to 0.02mm
You want zero to truly be zero. There are other ways to do it, but having it be zero is the best way. The fewer tweaks you have over here to fix an issue over there the better Tweaks tend to get overlooked when you change things around. Once you are printing, the print it's self can tell you a lot about how close you are and how level everything is.
