What says this universe supports kai energy? You need to come to terms that this universe may NOT support the energy that goku and vegeta weild, and it will be useless then. They've been through different timelines of their universe, but interdimensional travel is more complicated. The laws of physics in one place cannot exist in every plane. If in the destiny universe kai energy is unusable, then that renders saiyens no more threatening as a dreg. In this situation the guardians would win hands down as they can wield the powers of light, and the darkness that of dark. Goku and vegeta cannot weild light or dark energy, and they would perish.