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.
I can't make the "antimatter has antigravity" idea work easily. The motivation is that when you collide a massive hadron with its anti-twin you can get nothing but photons and vice-versa. Each half produces the same thing.
Morrison's argument is appealing. I mean why should gravity attract something that is 1/2 matter and 1/2 antimatter if it is supposed to have zero relativistic mass here? I guess the acceleration-deceleration energy required to reattain zero relativistic mass (or at least zero kinetic energy) at a further distance is the thermo 2nd-law problem with the conservation violation alleged by Morrison.
All the mesons and bosons are 1/2 matter and 1/2 antimatter, I think, but they can have zero (massless bosons) or non-zero rest mass (mesons, composite bosons).
I've often suggested that orbiting photons should have a rest mass, and that's what seems to complicate things for me when trying to rule out antimatter antigravity.
Photons are bosons (force carriers), of course. Light evidently doesn't distinguish between matter and antimatter. The photon is supposedly its own antiparticle, which fits in with it being 50/50 matter-antimatter. The hadrons are mostly quarks though (3 of them), and they're either all matter or all antimatter. I want to look at each quark as 1/2 matter and antimatter, to build them out of bosons that gyrate such that the matter part is either exposed or covered.