I started out with Blu, wasn't impressed. So Dr. Google was asked. I found several forums and started reading. Ended up with V2. It's v2cigs.com, I think. My experience with them is good, nice customer service, free shipping and you can try out the oneway first, or get a battery, a charger and their variety pack, one of each flavor, to pick.
I found the refill of the little tanks with their eliquid is much better, taste wise, than the cartridges. And you can use other eliquids, are not forced to buy theirs.
It's basically trial and error. But as a guideline, their "Red" is pretty close to red cigarettes, strength depending in nicotine content.
As for what it does to your lungs....I was coughing for a week. But can't say for sure that it was from the cigs or farming on dry fields (lots of dust) lol. Now I'm feeling better, have much more air and no more cough. I suggest you read some forums, lots of info on ingredients etc out there.