PG has a better throat hit and carries flavor better.  VG produces more vapor, but reduces the thoat hit and reduces the flavor.  The higher the nic, the better thoat hit.  I know some flavors seem like they have a better TH, not sure if stronger flavor would increase the TH, but I could see that it could maybe??  if 18 is not doing it for you, try 24.  and if you want the best possible TH, then do 100% PG, but most people after they've been vaping a while seem to like to mix a little VG in there.  20% VG, 80%PG seems to be the most popular, but its all personaly preference.  There are TH enhancers out there, like vape wizard.  Also putting a drop or 2 of pure menthol per 1 ml of liquid will also increase the TH without making the juice taste like menthol.  Sweet-Vapes is very popular and a good place to get juice.  Only thing I can reccomend is spend the extra $$, and get a couple different configurations in the same flavor and see what you like best.