They know there are other worlds, they can get to ones similar to Astlan, with similar magic systems or at least non-contradictory systems.
They [b][i]might[/i][/b] be able to get as far as Greyhawk or Morrowind but I think that would be really pushing things. Arduin is a slightly more likely limit, if it even still exists.
Not clear they could ever get directly to a high tech world…they might get to a steam punk world though.
Hmmm…what about a War Hammer 40K world? Now that would be interesting.
Anyway, according to the documentation in the library (here) all the worlds the wizards can get to have very close to the same rules of magic.
Now, that’s talking direct spells. Indirectly, via the Astral Plane, they can of course get to places like Earth. The problem would be, could they “land” on it. Not clear that their magic would let them. For one thing people from there don’t look like people, they look like unbound demons.
This is the distortion effect, and I assume it works both ways for them