I'm discovering that it's a science to learn the sweet spot while using the Evod.
Each juice is different and requires its own tweaking. Although the 3.7V battery that comes with the Evod is the perfect battery for the product, getting a VV battery is simply a must if you want to experience juices the way they are meant to be experienced. By adjusting the VV ever so slightly up and down while vaping, you can find what the perfect voltage for that particular juice is, and you can make a note of it so that you can adjust it accordingly the next time you fill your tank with the same juice. Right now I'm just keeping that information at the top of my head but eventually I will probably keep a little diary of notes to refer to as I collect a wider selection of juices from various vendors.
I've also found that the third wick in the Evod is completely useless. All it does is make it harder for the juice to get to the coil. Although this is especially true with high VP ratio juices, I've found it to be true to a certain extent with all juices I've tried—it simply takes too much time for the coilwick to get saturated, too many dry hits, too much chance of burning if you overuse it. Taking one of the flavor wicks out is extremely simple and if you're careful, it can even be done with a pair of tweezers without even taking the head apart. With the third wick out of there the flavor and vape production doubles, and if it is a thin juice you can simply turn down the voltage a little.
I'm also experimenting with different ohms but have not had the opportunity to compare enough of them to use that in my formulation of the sweet spot, though that will certainly become a factor in the future I'm sure. I've also learned that the only way to switch flavors is to give everything a good cleaning and dry burn first. If you don't do this, it will take forever for the often nasty taste of the two juices combined to disappear, and you actually may never experience the new juice's flavor the way it's meant to be because there will always be remnants of the previous juice, gunked into the wick.
So there you have my meager attempts at discovering the sweet spots for an Evod. I hope this helps out other newbies like myself avoid a disappointing vape and enjoy the juices the way they are meant to be enjoyed.