I had mine built to 0.5 ohm, which wasn't low enough for a mech (really cool, no flavor). That build was great at 50W on a
sigelei 100 W though.
So if you're going mech I think you're going to have to shoot for more like 0.2 ohm.
For a DNA30, I think I would do dual 28 gauge, 2mm ID, 7 wraps each and run 25-30W.