Hey Regan ...
Alot of its trial and error. 2 extracts with the same ingredients can have completely different outcomes.
Flavor #1
80% PG, 10% Water, 10% Natural Flavoring = Chances are, this will smoke well because of the amount of PG.
Flavor #2 (Remember, same flavor as #1, just different % of ingredients)
40% PG, 30% Water, 30% Natural Flavoring = Pretty high water content, and lacking in the PG area. This one is likely not going to smoke well if at all.
Try the samples and see if they work for you
Good Luck