Ya, longer dwell makes you quieter, but also uses more air.
Each time you change your dwell, you should readjust your regs as well.
If you want the smoothest shot possible, then you'll also want to run your LPR as low as possible. Just set your velocity, then turn your LPR down until it's at the lowest setting it can run at consistently under rapid fire.
Black/Purple Spire F/s. Freshly updated from Virtue.