Be sure to check your machine's manual. We can only tell you what we do for our machines. I have a Pfaff. I can use my IDT (walking foot) with all my decorative stitches. I cannot use the IDT with my FMQ/darning foot. I only have to adjust my tension for very heavy or very light fabrics. A medium setting works well for piecing and for FMQ. When I lower my feed dogs, my stitch length is mute so I don't bother to change it.
Practice on a sample sandwich, do what your manual says, then play with the settings until you figure out YOUR machine.