I don't really think it matters whether you get live rock or dry rock in a FOWLR, but I'm not an expert on FOWLRs. If you want some crazy aquascapes you can get puccani and chisel it into awesome shapes like caves and arches (and it's much more porous than fiji rock, so it gives better filtration), but for most people fiji is fine.
I would say you are better off with dry rock. Most live rock contains lot of unwanted creatures that can pop out at any time. If you don't get good live rock from a reputable source you can have these issues. But even with dry rock you must cycle tank before adding anything.