When both toggles are down, you are in the lightest gain setting. Amp-like chimey breakup.
G1 flipped up adds a touch of drive for more riffy grit.
G2 flipped up puts you almost into distortion land, with more saturation and sustain for lead tones.
Both toggles flipped up sends the Kilt V2 into almost uncontrollable gated fuzz/distortion that will cut through anything. For the V2 JHS added the ability to switch the G2 toggle with a Red Remote. This gives you the ability to flip into heavy overdrive or fuzz with a footswitch on the fly, making the V2 just as versatile as the V1 but more compact.