You can generally see what the Bit Optimization setting will do in Designer, before you actually carve. The attached images are of one of the built-in patterns, Basic - Composition - Crest 01. The first is with Bit Optimization: None and the second Bit Optimization: Best. Because this pattern has some fine detail and is fairly deep, you can see a significant difference - look closely at the center of the pattern, and at the upper edge, as you toggle back and forth. With other patterns that have less detail, such as Basic - C Fillagrees - C Filagree 01, you will not see much difference.