Great advice from Jon, as always.
The HG2 is a 20A cell. It's excellent at what it does. Hugh drain with a great capacity.
Going strictly by its amp rating of 20A (LG does not spec a pulse rating for any of its current cells) you can go as low as 0.21 ohms. Some prefer not to go as low as to hit the amp limit of the cell. For me, I'd use that cell at that res, no problem.
Other great cells for you would be the Samsung 25R, LG HE2, HE4, or if you want a bit extra safety margin, the LG HD2 is a 25A 2000mAh. Like Jon said though, most if your builds sound well suited to the HG2 and you'll get much more vaping time.