For a hassle-free vape, I truly would not recommend tank systems - at the worst, I've had many heads on tank systems taste burnt and acidic right off the bat, with 0mg juices and juices that are proven to wick well, and at the best, with extreme manipulating and taking risks and chances, I've gotten a vapor that is tolerable but always has an undertone of a wicky taste. CE5's, Kanger, Smoktech, Aspire, Innokin, I've had nothing but bad experiences from these tanks, and I don't believe there's anything "simple" about them.
I've literally found that there are some rare, off-brand cig-alike kits that have more consistent flavor, and to me, that's really important over anything else. I can have a ton of vapor, but if something tastes unhealthy about the vape, I simply won't vape it. I've also gotten a very good flavor experience out of the Cisco 3.5 atomizer (the cheapest version - $8.99), and while it was working, it was honestly one of the simplest devices I used - all you do is take off the drip tip and drip a few drops in, the flavors don't even bleed when switching. Problem is, it gunked up in 30 minutes, and was impossible to clean.
I've decided that my next attempt will be building microcoils that allow me to fire the coils before sliding a wick in (to allow for oxidation, or whatever), that allow me to exchange a wick in the blink of an eye if the wick happens to get burns, that allows me to not spend $3-5 on each broken head I buy, and so that I can monitor the state of my coils. The heads that I buy, they always come in either cross-wrapped, or heating-guard will be caught all in them, or they'll be touching metal, or they'll be wrapped way too tight. It seems like no pre-made head has a quality standard that I can agree with - and the rare times they look perfect, something will still taste very odd about them.
If I end up getting a great taste from my own coil, I may eventually try for cartotanks, but from what I've read around the forums, it seems that cartotanks can be really, really tricky to get to work, and that all brands suffer from some make problems just like anything else. I never thought that I'd be the guy to get into building, but I gotta say, the performance of all the heads and coils I've tried is just... anywhere from horrific to very low standard. At best, at absolute best, the coils perform in a way where I can't taste much in terms of nasty tastes, but that I can't taste any good ones either. That's the best it's gotten.
So right now, I know it sounds like an impossible task, but if ya'll are anywhere near as focused as I am on ensuring that your vapor tastes nice and clean, and really gives you a standard flavor with your vapor (for example, blueberries tasting like blueberries, and not sweaty socks), I haven't found one product that even begins to have a quality standard to match a vaping lifestyle, at all. It's bad enough that before anyone buys I tank, purchase three different packs of heads from three different vendors because at least two packs will be bad. That's been my literal experience.
Other than that, the only things I can say is to try what I haven't, carto-tanks, or try what I'm fixing to, rebuilding. If you absolutely do not want to consider those two things, you really can easily test out your preference by buying some CE5's. They seem to have just as solid performance as anything else, and if you can't get them to taste right by following the instructions, then chances are, no tank will work for you, because they're all essentially the exact same coil and device. They're great, easy ways to test and see if you mesh well with the standard and tastes of these vapes.