Nope bro, these connector clip dun snap open easily at all. Besides, for mine I secured the both end of the strap with thick beautiful nylon string, won't come out so easily one.
I used both the external clip for my camera, so the snatcher must be "pro and fast" enough to unsnap both the clip connector on the camera before he cabut, which is quite impossible because even I still have trouble unsnapping off when I wanna keep the camera myself even though I have used it for more than 2 months already.  

If the snatcher really wants your camera, he tarik hard hard also you have the possibility to injure yourself the middle of the process one. So no matter what strap is used, when you are targeted, you are basically in danger after all.

Depends. If you are shooting at 1/300sec or faster, then no need VR.
If slower, then sure crucial lor.