When you scrog the main idea is to make a flat and even cannopy, i'm quite sure just LST is the best and quickest way, i' would even say dont bother about plant count and put like 9 plants in there no topping at all just LST, i guarantee you more plants less stress means more yield in less time. BUT if you must go about topping it's for much the same reason : more lateral growth. the more you top the more lateral growth, 8 mains takes time that's what i dont like, but you'll be able to fill the net at least, which is the main point of the SCROG. More even is better though so whatever your technique , just fill the net up . Hope this helps ! 🚀