If your at an ohm that's only about 15 - 18w.
32g would really surprise you. Instant heat up. I wouldn't go over 28 unless you like long draws and heat up times.
A parallel 32g spaced coil would be my first choice. I ran that for a long time and was the best, and fastest performer at 15-20w. Or a single, 2mm, 30g, spaced coil at an ohm, or 28g the same. 28g will take the longest to heat up at an ohm on a mech.