My understanding is that maximum speed is defined when going through space so light speed is maximum speed while going through space.

But I think theoretically we can defined travel through spacetime (or by transforming space itself) or something similar where a distance can seem to be travelled at higher speed than light is measured as space. I am thinking about this as I heard that when thinking that our Universe expands so each two galaxies lets say depart from each other will eventually speed up “faster than light” in the sense that the space itself expands.

Or I can be very wrong so please correct me.

Disclaimer: uneducated ignoramus posting.

Does that apply to wormholes, assuming wormholes are a thing and we ever develop a method to warp spacetime arbitrarily?

Wormholes aren't true FTL travel, they change the geometry of space such that there's a new shortest path for light to travel from A to B. Setting up a wormhole between two points requires slower than light travel to extend the wormhole ends. But after initial setup it would still be amazing :-)

If you're interested in some simplified-but-still-roughly-rigorous discussion about the physics of time travel/causality, Sean Carroll did a solo episode of his podcast where he talked about a few different ideas in this space.

https://www.preposterousuniverse.com/podcast/2020/11/23/124-...