Yep. The Hydro Copper is just a GPU capable of taking liquid cooling; it doesn't handle the liquid. Just get an air model unless you want to go for the aesthetics of liquid and are willing to do a whole lot of research.
Yes, you can SLI reference and OC boards. If I'm not mistaken, they'll have to run at the same clocks, though. This probably means OCing the reference board as much as possible and then setting the OC model to match.