The NVS is the slightly softer, slightly higher torque brother of the NV.

Most players will tell you it's definitely softer - I've read plenty of reports of players equating the NVS X with the NV S. However, shaft profiling graphs show the shafts to be just that - the NVS slightly softer than the NV.

The thing that largely differentiates FW shafts from Driver shafts is that FW shafts tend to be heavier.