Perfecting NET's can be a fickle mistress & requires some finesse. I experimented with NET's shortly after I started doing DIY as I wanted a more authentic tobacco flavor & experience from my juice. I used M-Red tobacco as that's what I smoked (not the best choice of tobacco due to all the harmful chemicals, I only choose this as I was still trying to refrain from smoking at the time, IT WORKED!) & extracted it in 100% PG. Due to the lower viscosity PG works WAY better for NET's than VG, not to mention higher PG ratios just work much better for tobacco flavors in general. Although you can use VG, unless you are allergic to PG I would recommend using 100% PG or the highest ratio of PG your comfortable using for NET's.
When you do the extraction you want to keep the PG/VG really warm but not hot, I would say around 150*F or so but if you get it too hot it does something bad to the tobacco & produces undesirable results, at least in my experience. When I did the extraction keeping the PG really warm but not hot it produced a really authentic tobacco flavor & experience, it was a very satisfying vape. When I did the extraction with the PG hot it seemed to "over cook" the tobacco & produced a very bitter, burnt kind of flavor, again in my experience. I only did NET's a few times & as such I am no expert by any means, I'm just relaying my method & my experience.
As I stated, commercial cigarette tobacco isn't the best choice for NET's, due to all the horrible chemicals/additives they contain. A much better option for NET's is to go to a cigar store like Briar Patch & check out their "aromatic pipe tobaccos", they have some really rich smelling pipe tobaccos that work great for NET's. Smell the tobaccos & choose the one's that smell good to you, the aroma they produce will play a big part in the flavor they produce in your extraction.