630mm bars are already very narrow for a modern mountain bike. I would not recommend cutting them at all.
Most full suspension bikes are coming with bars that are ~750mm, and relatively short stems (<90mm).

With a mountain bike, the wider bars provide better control, and give better leverage. Your fit should be with relatively wide hands and elbow bent outward. If you feel that the bars are putting you too far forward, you may want to try a shorter stem.