Hi parapo - I haven't played around with them that much to be honest. I'm still waiting on my flavourless liquid and some
tobacco absolute. I mainly got nutty flavours with a view to experimenting making something a bit like 555.
The flavours I have tried so far are coconut, cocoa, hazlenut and cola. The don't seem as strong as I originally thought they would be so I would start with them being 15-20% of the recipe. This could vary from flavour to flavour though, I haven't tried enough to say yet.
I've been mixing up batches of 20 drops and working out the percentages from that. at the moment the nicotine content has been very low so hopefully the flavourless liquid will spice it up a bit.
Let us know how you get on. I'd be interested t know what the difference is betwen those vanilla varieties.