Hey UG
I have a peavey JSX which you may or may not know has a reasonably good built in noise gate.
I'm just wondering if having it turned to about 3'o'clock AND having my boss ns-2 on will interfere with the ns-2 at all?
or doesn't it really matter?

Also what kind of settings do people find work best with the ns2? preferably for metallllllllll

Are you asking because you already have an NS-2 or want to get one? If you already have one - then try it out and find out.

If not - the only downfall might be a little tone-suck. Most built in noise gates aren't that great so I'd get the NS-2 anyway.
ISP Decimatooooor
Carvin V3 - Matamp 4x12 - VHT Valvulator - Maxon OD808 - Visual Volume Pedal

EH Cathedral - Ibanez DE7
I would just turn the built in gate off and run the NS-2 in the X pattern hook up. If running both works better for your purposes than run both. As long as you are satisfied with your tone its fine. You can't do damage to your amp or pedal.