DDJ 1000 beat grid

So it's possible to play live in Performance mode and also adjust the beat grid?

What visual feedback would I get and what screen?
Can this be done in rekordbox itself using the Grid menu?

Yep, hold shift and turn the edge of the jog; you'll see the grid sliding on the screen.

Is there any audible feedback like a metronome through the headphones to hear the beats or is it simply visual?

You could enable the metronome in the grid edit mode. I wouldn't do that while playing live tho!

So I could use the grid edit mode in rekordbox while playing live?
And the track's grid, cue points, etc. would be updated to the DDJ on the fly?

Yep!

Would the metronome sound come through my headphones only?

Correct.

Will this work with the CDJ-2000NXS2 as well (using the browse knob instead of jog)?

When I can afford I'll be buying the NXS2 setup again and wondered if the beat grid could be adjusted on the fly while in Performance mode using the CDJs and if I would be able to hear the metronome in my headphones.