Oh please.... an order of magnitude is not a matter of taste. Sure, tastes differ, but they don't differ that much.
I use almost an order of magnitude difference when making juices for different devices, so it could indeed be a matter of taste ... + vape hardware + etc. I haven't seen many manufacturer's recommendations, but most or all seem to be for their whole line. Meanwhile their flavorings vary a lot. But their starting number is still useful. Any source of a guide you could name still could need a conversion factor and case-by-case adjustment.
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I haven't tried a Nautilus 2 with .7 coil, but a regular Nautilus, at least, is low enough power etc. it needs fairly full flavor. It's a good point that one tends to move towards less flavoring and I love some very light flavorings, but devices do vary. When I was testing and buying ejuice at vape shops for high prices I wanted to be blown away. DIY allowed me to get more into subtle mixes, also they just seem to be easier to make good. I still buy some juice for my real sippers, pocket devices -- the question is usually if I'll finish a bottle before it goes bad. I'm better off aiming DIY at a different kind of flavor range with an almost clean break from my older favorites and hardware.
It is good to try your flavors as a single flavor mix. This eliminates flavors you're just not going to like or would have to be secondary. Some flavors just don't vape right by themselves though. This can be a lot of work to try everything. I use a dripper and try different flavors without rewicking and can tell a lot by how they cut across the previous flavor and take over. How they play with others is a factor anyway. I use my juices in a freeform mixing for most vaping. I've been mixing different flavors together since almost day 1. After all this testing, I have a big pile and still try new flavors, but really don't use that many regularly.
The flavorings are designed to be used in various foods including candy, mixing it with large amounts of sugar. Thus, they're not supposed to be pre-sweetened. VG does have some sweetness but relying on that means you need low flavoring. Some flavorings seem sweet but it's more a flavor that we associate with sweetness, like ethyl maltol. Some people are OK with this but others are going to need some real sweet behind it.
