Bubblegum pop does NOT refer to the Backstreet Boys or NSynccheck the link if you doubt that Bubblegum pop is the teen stuff from the late s and earlymid s I dont know that I would exactly call it a subgenre of power pop but its certainly a related genre Goody Goody Gumdrops by the  Fruitgum Company Love Grows by Edison Lighthouse Fox On The Run by Sweet and just about all of the hits by the Bay City Rollers would be considered classics of both bubblegum pop and power pop