I mean in the amount of energy it has and in its size. That which is observable is apparently only a sub-universe. It seems to be limited only by physical laws, but even those laws could be different in other sub-universes.
I don't know about any differences. Particle physicists don't have much of an opinion on gravity and on uniting gravity with the other forces.
A proton and neutron can still have three quarks each with some of them being matter quarks and others being antimatter quarks. The strong and weak forces can be manifestations of gravity and electromagnetism at short scales, and electromagnetism could be a manifestation of gravity and anti-gravity, but particle physicists generally do not concern themselves with such ideas.
"The equivalence principle - If one can invent a theory in which matter and antimatter repel one another, what does it predict for things which are neither matter nor antimatter? Photons are their own antiparticles, and in all respects behave exactly symmetrically with respect to matter and antimatter particles. In a large number of laboratory and astronomical tests, (gravitational redshift and gravitational lensing, for example) photons are observed to be attracted to matter, exactly in accordance with the theory of General Relativity. It is possible to find atoms and nuclei whose elementary particle contents are the same, but whose masses are different. For example, Helium-4 weighs less than 2 atoms of deuterium due to binding energy differences. The gravitational force constant is observed to be the same, up to the limits of experimental precision, for all such different materials, suggesting that "binding energy"— which, like the photon, has no distinction between matter and antimatter— experiences the same gravitational forces as matter. This is again in accordance with the theory of General Relativity, and difficult to reconcile with any theory predicting that matter and antimatter repel."
If light acts the same way around antimatter, but matter doesn't act the same way around antimatter than around matter, then light going from matter to an antimatter singularity has a conundrum. How can the light act the same way with respect to the source and yet differently from the matter with respect to the antimatter singularity? The light wants to be sucked in to the singularity and the matter wants to be repelled away? I don't think it can happen that way unless the direction of the light is reversed, but that seems to make the antimatter singularity a white hole, however it also apparently rules out any light being emitted by the matter, which makes no sense. Therefor I see no reason to treat antimatter differently when it comes to an alleged bipolar quantum gravity.