Some can, some shouldn't be topped. I don't know about bubblegum.....
I can't remember the thread or even who posted it. Someone on here showed how they were using LST on autos outdoors, might have been another forum I can't remember..... He would pull the main cola to the north and then pull evening else to the sides and south, this let his autos receive even amounts of sun without any shading. Pretty slick idea, I think he topped some too but not all, he knew which ones he could get away with topping I think.
I plan on try his method of lst on some autos in my green house, my neighbors have flood lights that won't allow me to flower photos.
Not sure how much help I am, but I thought I would share. That dude was pulling some pretty big yields with his method.
Maybe Google topping your bubblegum and see if anyone else has topped that strain for results. Good luck.