why top? depending on strain sometimes they dont respond well. you have height limitations? lst works just as well, sometimes better.
i would wait around 3-5 week to do it, that way i can see how the lower branches are coming in. if they "hug" the main stem and stay short, that will be a plant that wont be a good canidate for topping since that indicates a large main cola.
i defintly would wait to do it on the Shiva skunk, a NL pheno could give you the large main cola (baseball bat look) "Shiva Skunk stays tight and compact with her cannabis seeds"
the Sage will probably do better off with some training, they can get pretty big. i would look more into lst than topping though.