Here’s my nooby question.
While researching popular recipes here I see many people mix same flavours from different manufacturers, often in different proportions.
For example
Vanilla Custard (Flavorah) 2%
Vanilla Custard (CAP) 3%
or
Butterscotch (Flavorah) 2%
Butterscotch (FW) 5%
What’s the profit doing this? How can this method affect the final liquid?
Flavors from different manufacturers often have very different profiles. Where one might be lacking, another one might be able to fill in the blanks. You’ll see this a ton with strawberries. There might be one for the sweetness, one for the earthy notes, one for the realistic flavor, etc., and together they make the perfect strawberry.
It can also help by creating a stronger flavor overall without using a high percentage of a single flavor. Sometimes when you use a flavor at too high of a percent, you can’t taste it at all anymore, or undesirable tastes come through. If you break that flavor up and use smaller amounts from several manufacturers, you’re less likely to have those problems.
As far as the different proportions, in your examples flavorah is lower than capella or flavor west, probably because flavorah typically has more concentrated flavors than those other two.
We generally do this to get a “truer” flavour. It’s done quite alot.
Example, vanilla custard (cap) 5% & (fw) 2% would be their preferred mix for their custard in a certain mix or a stand alone custard.
If for instance you wanted a strawberry flavour, instead of just using a single strawberry flavour from one manufacturer, you could use a couple of strawberry flavours from different manufacturers giving you a truer strawberry that you prefer. This would be called your" (insert flavour here)base"
Because taste is subjective you would have to experiment until you found what flavour your looking for, but that’s the reason multiple flavours are used of the same kind.
You just beat me to it sis. 
I win! 
Lol. What patty and vapeymama said.
lol what Chrispdx agreed with what patty and Vapeymama said…
I agree with pugs who agreed with Chris agreeing with what vapeymama and Pattie said 
Ford makes a mini SUV
Chevy makes a mini SUV
Hyandai makes a mini SUV
Mercedes makes a mini SUV
etc.etc.
Each is different, each offers different amenities, yet some offer the same…
power windows, bluetooth, heated seats. etc.
But none equally the same, and then there is the cost difference.
One has more horsepower, one offers all-wheel drive…
Same marketing “label”, yet not the same overall.
If you could marry what you like in the Volvo, the Ford, the Mercedes,…
or whatever you like between any of them, what’s the profit?
You can then get what YOU prefer.
What an incredible solidarity 
The best answer, I’m good at analogys! 