Most current models of the universe suggest that it occupies a volume and has a finite number of particles. But these are just models based on observations and constraints.
There is no dispute that the observable universe is as you describe, but there is absolutely no consensus as to whether the universe is finite or infinite.
That's not true in the context of big bang cosmology. It's true that today we would not be able to observe things beyond the observable universe by definition, and so there's not much purpose in reasoning beyond today's observable universe, but the observable universe changes over time and when reasoning about the early universe there would be differences between a finite universe and an infinite universe.
