There may be 40 things called string theory, but they all boil down to a few things:
- point particles are actually vibrating strings
- there are extra spatial dimensions
- there isn't much in terms of specific testable predictions made by string theory
The LHC tests may show things that hint at extra dimensions (of small but testable size, not planck length). This in and of itself wouldn't prove any of the individual string theories. But showing nothing that could indicate super symmetry or extra dimensions or other 'stringy' things would be an issue for strong theory.
Disclaimer, I am not a physicist (string or otherwise).