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.
Hoag's ring looked so much like a diffraction ring in lower resolution. Coincidentally enough I suppose the center is a coherent gravity source, hence the obvious (heh) anti-gravity ring "focus" effect.
As noted before, that's a little red Einstein ring inside the Hoag ring, at about 1 o'clock.
I've suggested Hoag's ring-center mutual antigravity phase (in the dark region inside Hoag's ring) is what is doing some lensing for the (alleged) Einstein ring seen through there too. In that region, a rare exception of sorts it seems, negative energy more than slightly predominates, I suppose.
Maybe as a result of a negative energy effect on light passing through it, the Einstein ring is magnified. That's an effect that would be opposite to the effect of conventional gravity lensing. It's apparently somewhat evenly distributed over the object lensed, only slightly inhomogenous (only slightly axial) which is too complicated for me to explain at the moment, but I have some ideas, like a mixture of gravity effects and complementary antigravity effects. Anyway, the effect is apparently generated from the periphery of the line of sight rather than the center at the Einstein ring lensing object's location. The Einstein ring is rather spread-out and stretched along a radial of Hoag's ring, to my eye, anyway. A lesser amount of conventional opposing gravity running cross-radially is apparently what makes the Einstein ring magnified almost as wide. I see the dark region between Hoag's ring and center as a convex gravity lens, shaped much like a flattened donut. The region of that shape of lens transmitting the Einstein ring image has positive curvature in all directions, it's not behaving much different from a magnifying glass there. The entire antigravity-phase region is spherical, but much weaker at much distance outside Hoag's ring plane, where the ring doesn't reinforce it. That's how I see it, anyway.