(Please bear with me.) If the universe included multi-universes, and black holes transferred matter between them, AND yet there was a large, but FINITE amount of matter and space, How would that max-limit change our understanding/perception or theories of the universe? Would it make any difference or change current concepts?
You should do some research regarding early models of our universe as expanding, contracting, or static. A static universe has implications for the energy use in the universe.
Regardless most of the physics would be identical, only perhaps Relativity would be any different, as it is the only area of physics which deals with such large distances.