I think the only real constraints on an ASI would be what's physically possible. We don't really have any reason to consider that there could be a limit to machine intelligence, besides hardware. (And then we just get it to design better hardware.) Stuff that we know could be possible like nuclear fusion and FDVR would be trivial, it's only the more theoretical stuff like FTL travel that might be impossible.

But even a machine that's "only" 100x smarter than us would be a massive game changer. Even with narrow AI designed by humans, we were able to more or less solve the protien folding problem. Imagine what something that thinks at the speed of light would be able to do.