I'm pretty sure they didn't create the abstracts etc, as these things must have existed to be able to define the Beyonders as from 'Beyond' (if not, beyond what?).
But I think their creating universes and stuff is just random experiments that they have done at some points (like how they experimented by letting the energy into 616 that became the original child unit Beyonder).
Also if they created/empowered all the abstracts you'd figure they could very easily get rid of them rather than physically fighting them all.
+ everything associated with the Beyonders started vibrating at the same frequency a while back as a way to trap the Celestials/abstracts, so I'd say they're clearly not the creation of the Beyonders.
