There are still times to switch the electronics off and most notably that is when driving offroad or in deep snow. Even high speed dirt road driving should be done with ESC on. But regardless of your car's electronics, it's not worth the risk of disabling ESC.

When should I turn off stability control?

As a sensible driver, the ONLY TIME you would want to turn off traction control is when you're traveling up a steep hill where the surface feels loose because of gravel and stones OR trying to get your car unstuck from the mud.

Should DSC be on or off?

If DSC is on, it won't allow any wheelspin, and this can cause you to lose momentum on the hill and not be able to get up it. - Taking your car on the track. Turning DSC off will allow a little wheel-spin and allow you to get out of corners faster.