I do some handquilting, but I use the seam allowance as a quide to get straight lines. For the size of stitches, I started out by using Tiger Tape. Tiger Tape has lines on it, helpful in getting equal stitch size. But as beginner, try to get your stitches uniform in size. Meaning that the stitch and the space between each stitch is the same size. With practice your stitches will become smaller. I, too, use the stab method where seams meet.