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.
Etek 3LT grey/black f/s
Valken Proton greyish/black f/s
68 4500 PE stubby, LP output f/s
68 4500 AIR tank(no reg) f/s
Creed/demon eyes f/s