There are as many ways to do it as there are quilters. On my Tea Time in Tokyo quilt is FMQd stems and leaves between the flowers because I needed quilting there anyway. This might not work for another layout. Each quilt is different, so do it any way you like.
Since I don't enter contests or shows my rule for stitch length is simple. When I stand back 6 feet can I still see the irregularities? If not then most people will never see them either.
When I learned to sew 50 years ago I was taught to reverse stitch several stitches, then forward stitch. The over-stitching locks the beginning/ending in place but blends with the other stitches. I still like this better than 1 lump of stitch-in-place.