If you are looking for clones, I like to top them around 8 nodes...so you can leave four shoots on the stem...if you don't want clones then pinch them around 5-6 nodes....pinching is easier on the plant, it doesn't slow growth....
wait 2 weeks inbetween pinchingn/cloning and before flippn the ladies....that gives time for the shoots to devolp fully, in veg youi'll get weak clones, if you go right into flowering you will get funky noding if you don't give the plant time to rest after pinching or cloning
Look into the "FIM" method of topping and learn how to bend/train your plant to grow to recieve the most light and fit your space and in most cases optimize yields