For some of us, yes. Extremely important.
For instance, some of us have sensitivity to PG (in varying degrees), so we have to cater to (or address) that first and foremost. Some experience a tightness of chest, etc, it's effect on me when using beyond a certain percentage is "waking up with my mouth glued shut" (so dehydrated that it makes it both hard to open my mouth, and hard to breath). The severity for each person is different, and directly affects how they have to mix.
It's then that choice of flavors becomes even more important (or limited) due to the percentages required for some flavors or vendors (FW and TFA often fall into this bracket sadly) to achieve the desired taste/results needing to be in higher ranges of 8-12% (or more, to some tastes and/or hardware combinations). So in example, if I have to stay at (or higher than) an 80vg minimum to avoid "glue mouth", and I want to make a semi-complex recipe (4 or more flavors) then I'm probably going to be SOL by the time I got to the third flavor (if using all FW @8%) as I've already exceeded the 20% margin for flavoring that I have to stay in.
As for effecting recipes, again, a resounding yes.
As you continue delving further down the rabbit hole, you'll learn that hardware makes a difference in how your mixes are "processed" (or delivered).
For instance, a mod that doesn't provide consistent regulation can yield highs and lows in power delivery in a single "puff" (how long you hold the fire button), and the longer the drag you take, the more it becomes noticeable. Easy for me to notice because I take 5-7 second pulls on average. Whereas those who do monster high power seem (more often) to do shorter blasts. There's exceptions to every "rule" though, but the key is in understanding the variables first, and then you can apply them. And that's just with mods. Same can be said for batteries. Different ones respond in different ways (deliver power differently).
And then there's the atomizers.
Generally speaking, it's generally accepted that:
- clearomizers (or mouth to lung or MTL tanks) require more flavoring than a restricted lung tank would require.
- a restricted lung tank would require more flavoring than a direct lung (DL) tank does.
And then things start to get a bit tricky.
Some DL tanks are awesome by design for flavor (such as the Aspire Cleito), and will almost deliver an experience similar to a RDA. Others more closely respond like a restricted lung hit. So there's some leeway to juggle (and adjust) for given performance disparities.
Then you have RDA's. These are the most, again, generally speaking, flavor friendly. In so much as, they require the least flavoring (percentage-wise) yet deliver the fullest flavor taste, and are much more tolerant of high vg content due to being able to supply an immediate and unrestricted supply of liquid.
Tanks have to fight for their supply, through all manner of delivery holes, size of hole restrictions, number of holes, sealed vs vented liquid supply chambers, etc. All dependant upon the design of a given tank. And as a result, the tanks typically prefer a thinner liquid to help facilitate the feeding process. But it all hinges on design.
I know this is a lot to soak in, and I apologise for it turning into a novel, but I vote this helps you understand some of the interactions, and why you'll see certain things as you progress!
Mixing your own base is just as easy as mixing flavors though. Don't let it intimidate you, as you're doing the exact same thing. Do be respectful to the nicotine though, and always use the proper safety gear, and handling techniques though!