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.
This part of what I quoted is the most interesting part to me at the moment:
"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."
We can say the photon is half matter and half-antimatter and the binding energy has a photonic equivalent, which I think perhaps obviates this question. "Matter" itself is not pure matter, it's partly antimatter. These concepts are not easy for most people to juggle.