Depending on strain, some respond well to topping/fimming others not so much. If I've decided to top a plant I do it right at day 14 or 15. Once they are in week 3 (FastBuds strains) they're getting ready to, or are in pre-flower and I don't screw with them except to LST the hell out of them. I've not grown this strain from Sweet Seeds before but on past Auto runs I've tried different methods on multiple plants of the same strain to see what they like...or don't. On yours, I'd just LST the hell out of them and keep them happy!
Good luck! Can't wait to see the finish!😎👌