If I'm researching right, the popular combo seems to be the Ego Twist and Evod Clearomizer.
What this entails battery wise having a battery that is cigar-sized, with a small knob at the end that controls what is essentially the power of your battery. It's a bit like temperature on an oven. You adjust this A. Because different juices "boil" better or worse at different "temps", B. Because the material that boils the liquid gets coated and clogged with burnt residue if heated too powerfully, and C. Because many users try to push this as far as they can because a higher voltage equals a more realistic throat experience. Also, the Twist is a big battery, it'll last a darn good time. If not, I believ someone said it has a "smoke-while-charging" chord you can buy.
What this entails clearomizer wise (the section that holds the nicotine liquid) is having cheap and replaceable "barrel" that screws into your battery, which you easily (with this model) and manually fill yourself, with flavored nicotine liquid. This is preferrable because A. The vapor lasts longer without changing anything, being 5x bigger than anything a regular e-cig can dream of holding, B. Having a clear element to the barrel allows you to see exactly how much liquid is left, C. Because the Evods are quite frankly made very well, D. They're cheap in comparison to disposable cartomizers, E. You can take every element of the thing apart easier than any other brand, allowing for extremely simple adjusting and cleaning, F. THOUSANDS of ingredients, flavors, and textures of nicotine liquid to choose from, and G. Though these are $7 per "barrel", they are washable (or completely replaceable if $7 is fine for you) and should last a very long time, the only thing you should probably replace with each different-flavor re-filling, or say, weekly cleaning, is the internal "heaters, which are $1. Certainly cheaper than $15 per pack of half broken Blu cartomizers.
It sounds like a lot to take in. But trust me, I've tried about 6 different "normal" e-cigs now. Literally all of them seem to break out of nowhere after 6 days, have burnt, poisonous cartomizers that leave you sick a week, or simply have cartomizers that are half broken and drain your wallet quicker than any real cigarette could. Quality control would make the "stylish, easy" devices actually worth it; when a Blu works, for example, it works. Not really much wrong with those when they fall in the %5 chance of actually even turning on. I just personally can't stand how much money I've wasted ($100+) on BROKEN products that the "easy e-cig" companies sell.
My motto is "So what if people notice that the quality, actually-working products are huge? Tell them it's an electronic hookah and they'll think it's much cooler."
I mean, really, I like the easy-go-lucky e-cigs the best, style wise. If Blu's products weren't literallt all broken, I'd love them. When they work, there's reallt nothing all that wrong with them. You simply have to get used to the fact that you get a buzz and feel by exhaling through the nose, not the mouth; learnin that makes cigs like Blu so much better. But simply, in this generation, brands like Blu don't even make products that turn on.