The thinnest line will be seen with a score at the proper material thickness as a height measurement.
However, now that you know there is an override for the height, you can have some fun.
Here is an experiment I tried, just to see how the results came out.
The big deal in doing a large project like this is two fold.
Faster design (can even be a hand drawn design scanned in).
And way faster score versus engrave time.