I ALWAYS carry an RBA all day... Usually a kayfun lite... I do have a kanga protank3 mini I carry as a backup... With a good coil and high wattage it won't output anywhere near the vape I get from the kayfun, but still plenty for a good vape when I can't re-wick or re-fill the kayfun easily... (i.e. driving down the road...) I use micro-coils in the kfl and cotton for wick, so when I need to re-wick it literally only takes me a few minutes... Pull the old out, burn off the coil, re-wick and reassemble... The coils, if well built will last a VERY long time before needing to be replaced.
Now as for the wattage... Here's the bottom line... More wattage = more heat... It's really that simple... Other factors effect how long the heat takes to build, how long it sticks around after being energized, etc, but no matter how you look at it, more wattage means more power, and more power means more heat...
More heat means more vapor... PROVIDED you have a setup to support it... Think of it like this...
If you run 100 watts into a coil and dunk it directly into fluid, it's going to vape like mad... and will continue to do so... it won't "burn" or get a bad taste... simply release a TON of vapor...
On the other hand, shove a wick through that same coil, and it's going to burn big time... Because the juice will instantly flash off and can't be "Replaced" fast enough... meaning you're now burning coil and wick instead of juice... That's a bad thing... LOL
In other words, you have to strike a balance... A given setup is only capable of wicking juice at a certain speed, based on the wick material, how much of it is used, the tank, etc...
So what it comes down to is this... You can increase your wattage to any point up until your wick/tank setup can no longer feed juice fast enough to keep up... Once that happens you're going to get that nasty burning dry hit...
What that means to you is this... The more wattage, the more heat... the more heat, the more vapor... assuming the wick doesn't run dry...
I can build a coil and wick setup in a kfl that can easily take 30watts... That means I can get a very warm dense vape and get giant clouds of vapor... At the expense of chewing through a LOT more juice... On the other hand I can run that exact same setup at 6 watts and still get a good vape... The only difference is, I'm burning off much less juice... so it won't be as rich, full or flavorful as running a higher wattage... My juice will last a lot longer though...
Does that make sense? Just because someone else builds a single coils and runs 15 watts on it doesn't mean you have to... it just means that potentially you can, which will give you a warmer vape and more of it...
When I vape from my kfl I'm usually running around 15watts... That gives a warm vape that you can almost feel in your mouth... What I mean is, ..... well... i don't want to say it's like drinking juice... LOL, cause i'm sure you know that stuff tastes nasty!!! but it's so much vapor it's like it almost condenses in your mouth a little and you get much more flavor out of it... And more nic... On the other hand, I can drop wattage and it'll just be a cooler "drier" vape...