DD sat the Wandsworth Test last year and said it was about the standard of the GL Assessment papers (NFER Nelson), maybe even easier.
She can't remember exactly, but thought to be 70-ish questions in 50 minutes.
The 98% pass mark for Graveney is kind of just a guide. It depends on what other classmates got for their score. DD knew a girl who scored 96% and didn't get in as she wasn't in the catchment and she had no sibling there. Those are also factors to consider.
The "two" NVR papers are explained thus:
Teacher (invigilator): The first NVR paper is nothing to worry about, it is just a warm up for the proper NVR paper, but your answers will still be marked for it.
DD said it was fine, just basic shapes like triangles with dots in the middle and so on.
The proper NVR paper is about GL's standard.
VR paper, once you've done one, you've done them all. Just need to brush up on vocabulary (not that difficult) and you should be fine!
Hope that helps,