Using these option in system.cfg and autoexec.cfg does indeed turn on dx11. There isn't really any difference other than the water, which has its own tesselation options. Nothing I've seen really stand out.
I don't know about r_driver honestly, but r_shadersDX11 is a real variable, it lets us know that DX11 can be implemented. I don't think there will be much of a difference. Was Crysis really that much different between dx9 and dx10? it didn't look that way to me.