Why may I ask did you find that funny? You asked and we tried to answer you. We all have different tastes. Most FA (tobacco flavorings) I use at less than .1% and yes I said point 1 %. I am not the norm most use from 1-3%. TFA (non tobacco flavorings in my case) I use less than 3% to even test them and believe me that is not the norm. But if everyone liked every flavoring at the same %s boy would that cut down all competition for ready mades and it would sure make DIYing juice so easy.
Yeah, there's a ton of variables that makes it different for everyone - personal taste, device, coil used, wattage, PG/VG ratio, not to mention stand alone Vs. as an ingredient in a blend
The suggested amount lists shared via links are a decent start to knowing at about what percentage could be used. It is all based on personal taste preference. As already mentioned, we all have different taste ranges which will affect overall flavor.
You may just find a recipe that will help you work out a general idea of how to ascertain a good starting percentage for a flavor you have question about. Try the recipe on its own and adapt from there.
Seriously, browsing through the recipe section and observing the percentages used will give you a good idea at what you can accomplish with a particular flavor.
Depends on the flavor and your tongue. Lol. I find "recommended" lists to be way off for my tastes. It's really trial and error. Make small test batches minus NIC if you use it. (to minimize costs in case the batch is bad/nasty)