When sourcing for flavorings, and when the vendor offers choices in extract or concentrate or oil form, what is best for vaping applications? I'm going to guess that oils are not the way to go, and it seems that the concentrates I've seen listed have a Gum Acacia base, so I'm thinking that's not what I want either. Just want to confirm that I want the extracts that use the PG/ethyl alcohol base...?