Maybe I need to take a step back and do one-flavor mixes at increasingly larger percentages to get an idea of what happens as intensity increases.
I'm not sure my wife would be on board with that. Whatever, it's worth it.
I started dabbing a drop on my finger, rubbin it in a little and then tasting it. Really opened my eyes not only to how strong the flavor really was, but gave me much more insight into the flavor profile itself and also the sweetness (fruits/candy flavors). It makes zero sense to me, but one will be sweet and the next will taste unsweetened. I've had a hell of a time until I started taste testing, then it just got a lot easier.
Second, if you are looking for % guidelines, just check out the recipes in the subforum to this one- you will see most tend to mix around 15-20% total flavor no matter how many different flavorings they mash together. Tobacco flavors tend to mix lower percentages it seems.
Mixing single flavors is always a best bet for getting a good feel for a flavor, as well as general experience with DIY'ing. Always remember, with single flavors, you can always hang onto something not vapable by itself, and then use the mix in another recipe.. the calculators out there can factor in the pg/vg ratio of the flavor mix you add.
oh yeah.. wizard labs does have the mix % recommendation on each flavor, in the description field... the only problem is that they recommend 5% for every single one of them... whereas my experience is that flavors vary wildly on mix %'s. Especially naturally strong flavors like mint, menthol, clove, cinnamon, etc..