None of us SMOKE zero nic.... we VAPE it.... lol.
Seriously tho, I vape some zero nic late a night sometimes, when I am having a conversation with other vapers/smokers in the "smoking/vaping area" before I quit for the day. I haven't yet cut my nic level down to zero on a perm basis. Hope I will get there someday.
For me, the higher the nic, the more TH. VG reduces TH and flavor, PG increases both.
P.S. One way to tell about zero nic is to order a "doubler" of you favorite juice. I often get 36 or 48 mg juice and cut it in 1/2 to end up with 18 or 24 mg. I may cut that further depending. Anyway, doublers are zero nic mixes that you could test. Just a thought.
If you have any plain USP PG you could vape a bit of that too. It may tell you something about TH (assuming you already vape PG with your juice).