My problem may be min & Max power?

From your photo, I think it’s a nice quality, but I also see what you mean.
However, it is unlikely to be your min/max settings because they will be visible all over your work.
One way I test my max/min settings when engraving is to engrave a square (in line mode) e.g. 50x50mm and adjust min until the ends of the four sides meet without visible difference.