If 100W is your absolute max and you won't get over that mark then it only depends on how deep the batteries are discharged by the mod. If it cuts off at 3.2V then you need batteries with at least 18A CDR, if it cuts off at 2.8V then you need batteries with at least 20A CDR (10% loss from the mod included).
If you need to re-compute because you want even higher wattage the formula is
maxWatts/(2*2.8V) = min battery CDR, then add 10% for losses in the mod.
The alien, also from SMOK, discharged batteries to 2.8V, so if we can't find out what the value is for the g-priv 2 then it would be better to go with that just to be safe.
Here are Mooch recommended batteries
Mooch's Recommended Batteries | E-Cigarette Forum
and here are his ratings for 18650
18650 Battery Ratings -- Picking a Safe Battery to Vape With | E-Cigarette Forum
If you go by the recommended list with your request you end up with either samsung 25R or sony VTC5A.