There is a bunch of research on the different alcohol molecules produced by different fruits, such as apple verses grapes, verses peaches etc... but it's not research for the public domain, as I don't think anyone has reported on these to the medias. Maybe not enough interest or the media can't decipher the research. I know I can't understand most of what I have been sent on the winemaking forums.
but, there are different molecules of nicotine as well. Perique for instance changes the molecules in the fermentation process to something not even recognizable as nicotine, and has no effects, but it increases the absorption of nicotine from the other leaf it is blended with.
Flue curing decreases the PH of the leaf, making it less absorbable through the membranes of the capillaries in the mouth, but more absorbable in the lungs, thus there is no accident that it was the 1860's when flue cured, French papers, and inhaling cigarettes began to happen. But, burleys having a higher PH is more absorbable through the skin, small capillaries of the mouth, etc...
Aromatics... the toppings change the PH as well, making them less absorbable, even if they start with a burley. of course there are different types of aromatics, some may vary.
I have never gotten a noticeable buzz from Virginias, in fact, I don't really fell anything. Throughout the day as I clench and smoke as I work, I am just tasting... but I am aware that I am getting some nicotine, just not detectable amounts.
And, most burley blends that use lighter burleys, I get about the same. There are a few that I feel a slight kick, like PS Cube Cut but blends like MacBaren Golden Extra might as well be all Virginias, IMO.
But, the air cured, fermented burleys in some of the stronger blends do mellow me out quite a bit before bed... and add in the stronger leaf, like malawi and dark African Virginias (which are not a true Virginia, nor flue cured) and a blend can have a much larger kick.
But, everyone's body chemistry is different and reacts differently top the different molecules of nicotine. And, I believe that if we looked closer at the nicotine molecule, we'd find that there is some other differences between them, as they are discovering about alcohols.