I think the 20w istick will work, but you'll be runnimg @ full or close to full power all the time, and the battery life will suffer. That's why I went w/ the 30w.
Unfortunately not. The original istick will not fire sub ohm....or if it does it's not far below an ohm...perhaps .9
How's the 30w working out? I decided on the 50w istick and waiting for it to arrive. My 20w gets plenty of use!