Excellent advice. Personally, a recipe that's less than 20%-25% just tastes like PG to me -- blah, bland, medicinal, just icky. But I wouldn't have known that without trying out a few "single-flavor mixes" at the recommended 2%, 4%, 8%.... and not been able to taste anything. My strawberry & cream is 30% flavoring, gunks like a mad mofo with all that flavor and sweetener, but it's so good... I don't care!
I've seen advice that more than 2% sweetener is terrible... but my S&C is 2.8%, up to 3% sweetener -- I usually mix it at 2.8% because it gets sweeter, the longer it sits; I just add a few drops more sweetener to the atty itself, when I first get into a new mixed bottle.
Really, the only way to know how to mix something YOU will like is... MIX IT. Taste it. Fiddle with it or dump it, and try again. There is NO one single way to mix anything, because we are all different -- my husband could eat a lb of fudge at one sitting, and I feel like barfing if I have more than one tiny piece. Try different brands of different flavors until you find flavors that YOU like; mix them with this and that and the other thing, until you have a recipe that YOU like. Reading other peoples' recipes is a good way to start learning, but until you mix stuff yourself, you still won't know. Fortunately flavors are a LOT cheaper than ejuice; it doesn't cost that much to grab a lot of flavors and start trying out different mixes.
Andria