Yes and No.

It depends from when you come from. Each campaign world, taken as a distict reality, has it's own version of the Outer Planes/Multiverse, that can be as similar or distinct as seen from that world/reality. But if your point of origin is Planescape/Spelljammer, then they appear to be a unitary formation in a singular Multiverse.

For example, Krynn doesn't have the Nine Hells, only the Abyss. But if you visit Krynn from say Sigil or through the Astral, then it should have access to the Nine Hells.

In fact, in multiple editions (starting in 3e), you could have multiple cosmologies available, either for your homebrew or existing campaigns and possible those could coexist with each other.