At least my Mac OSX was ignoring VSync setting, likely because of BeamSync which is the peculiar forced dynamic VSync thing Mac OSX does. On 10.9.5 Mavericks at least, playing in a window helped with that part, so practically that allows you to play variable FPS rather than forced 15/30/60 which fullscreen suffers from.
I'm not sure either what Smoothmouse does, I stumbled on it in a guide for CS:GO Mac OSX
http://steamcommunity.com//sharedfiles/ ... =347017860, and personally I had a feeling it helped with mouse input lag a bit, but then again, I never had such an input lag that I would've considered it unplayable to begin with.
I wish I knew what Smoothmouse does, I could try adding a similar thing in RWR itself.