I'e been trying to duplicate the tone quality that some of the top GJ players including Django get on their guitars. I've been tending towards heavier gauge strings for more punch especially on the bottom end, but keeping the string height reasonable (2.5-2.75mm at the 12th fret). I am using a Wegen pick that measures about 1.25mm in thickness. My guitar is a Shelley Park Montmarte with a slightly shorter scale (10mm less).
Am finding that the angle of the pick relative to the body surface is the key. The flatter the better it seems whereas 90 degrees ives a simple dreadnaught tone. Also, where I am picking in between the sound hole and the bridge is important - too close and its too twangy and too far and it is too dreadnaught. The sweet spot varies with string length - thus playing higher up the fingerboard means playing a little closer to the bridge. One can also control the degree of tone by varying the pick angle as well, at least while playing slowly.
I've never had these parameters really explained well in workshops or online lessons. I thought I would share these observations here and see what others have to say.