No they aren't, althought they could destroy a galxy by an slow process of destroying planet by planet, a galxy includes all the dust, stars, etc. And surely they can't destroy an star. So nop, they are not galaxy busters
Non canon or not we literally do see the Southren Galaxy vanish/destroyed in seconds. If you disagree with that you have to cite proof as to TOEI using time lapsed frames. We see the galaxy vanish/destroyed alongside a comment of Broly destroying the Southren Galaxy. That's all there is to it.
So logically anyone equal or greater in strength than LSSJ Broly should be able to galaxy bust. To me that means Super Perfect Cell and above. However, I just don't see SPC busting a galaxy. But then again at just a meager power level of 200 Master Roshi destroyed the moon. And SSJ1 Goku's power level was stated to be 150,000,000. So how many moons can 150,000,000 destroy? 750,000. That's not the mass or volume of a galaxy by a long shot.
So even though logically in the non canon universe anyone LSSJ or above in power level should be able to bust a galaxy I just don't buy it. Maybe that's just an attribute of LSSJ. Maybe it just doesn't have a limit and given enough time could surpass SSJ3, Mystic Gohan, and SSJ Vegetto levels. But this is all PURE speculations.