Hard to answer without some additional information, so I'll start out with some generalities. My opinion concerning the "harshness" that you spoke of might be attributed to the nicotine content being higher than you were used to and your getting a buzz after only a few drags. You are probably wise to reduce it to 18mg.
You said that you got a new eGo Twist, the variable voltage battery. Were you vaping at a higher voltage than the usual 3.7v? Were you using the correct resistance cartomizer at whatever voltage you were using? Using higher voltage on a low resistance carto would definitely cause harshness. You must match your voltage to whatever you are heating your juices in (cartos, clearos, CE2, atty's resistance - 1.7 oHm, 2.0 oHm, 2.5 oHm, 3.0 oHm).
Most juice vendors offer either sample packs or smaller trial sizes of their juices making it more convenient to find what your flavor niche might be. What flavors have you tried already, and which did you like or not like? There are tobacco flavors, menthol flavors, fruits, candies and deserts, coffees and teas, adult beverage flavors, some that don't really fall into any category, even so-called savory flavors that taste like meat.
What I did was spend a good amount of time reading the e-juice forums here on ECF for ideas and recommendations. You'll soon notice certain juice vendor names coming up more than others, so chances are those vendors might be the best place to start your flavor journey. Start visiting those vendors' websites and see what they have to offer and what might be more to your liking. Then, see what sample packs they offer. If not, are their trial bottles cheap enough to try without wasting too much money (around $2-4 for the smallest bottle is good).
Before too long, you should end up finding one or two flavors that you like enough to buy again in larger bottles. Be aware that some flavors need some time to "steep", or mature; while others taste good upon delivery. I wouldn't throw any juice away if you don't care for it initially; revisiting it again 2-3 weeks later and you might find your all day vape.
I don't drip, so I test new juices in the new CE2's, the 0.8ml ones. They don't have a carto filler to taint or alter the juices flavor, they generally can be emptied, rinsed, and refilled with another flavor easily. If not, they are relatively cheap compared to cartos and clearos, so I don't feel so bad if I have to throw one out.
When given the opportunity when ordering juice, I always request extra flavor. A 50/50 pg/vg mix is a good starting point, unless the vendor recommends a different one. It's their juice, they should know which mix is best and twhat previous customers preferred.
That's all I can think of at this time, in a nutshell.
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