I mainly use a small stitch length blanket stitch, it makes it easier to go around the corners, it holds the fabric down better.
However, I just did some trees and bushes. I used a decorative stitch on these, it gave the edges a more natural look.
If I have several layers of fabric, I prefer to use elmers glue around the edges and heat set with an iron. It keeps the layers more flexible feeling, because it washes out. This worked well in the trees and bushes, I FMQ them down as well. If I am not doing as much FMQ I would use a steam a seam product.
Play around with your machines various stitches, adjust the widths and lengths. I use 1 1/2 X 4 inch strips on a bigger piece of 12 X 12 inch fabric. Do a stitch, mark down beside it, which one it is, the stitch width and length. Each project may need a different look. :wink: