SFML doesn't have such a relative mode (yet). But a similar effect can be achieved by resetting the mouse position to the middle of the window every frame and using the difference as relative movement variable.
As for GLFW and SFML interaction, I doubt it's possible. You can always try, but then you're left to your own devices.
Also please use the help section for questions. The bindings forum is really just for discussions about SFML bindings.