I am just kinda getting the hang of it or at least figuring out different things with PVC. The first thing that I do is setting the background color, if the object I want to focus on is dark then I make the background white and black if it is a brightly colored object. I believe PVC works off the level of light, so the darkest parts cut the deepest, I use the invert light toggle if the background is white. So you can edit your picture with a program like paint.net to lighten or darken any areas you want to raise or lower when you cut them. It's just as easy to make the picture a black and white photo and edit it after then. Most of the time I set the line spacing 10% but for bigger pictures I might go 14%. I almost always use a .125 inch ball nose, but that is based on the size of the project. If I was going to do the flower smaller I would use a smaller ball nose. I also set the cut depth at .25 inch for these two but I usually play around and see what depth I can get the most detail with or which looks best. The preview in PVC and Vcarve is really spot on.
For the finish on the flower I went with a clear polycrylic to keep the color of the wood. I haven't been wood working very long and I am not very good at putting on finishes on yet, so I was playing it safe lol.
I hope this helps!