Here's what I know and it's very little being a new vaper myself. My experience comes from the photo world as I do work as a photojournalist (among many other things)
In order for the police to detain (cuff) you they need reasonable suspicion. This basically means that if any reasonable person were to think a crime has been committed or that you are a potential physical threat that could put the officer in danger. Acting like a .... to the cops can elevate suspicion and cause undue stress on the situation. That's why if you explain things in a calm manner they have no reason to be suspicious.
Probable cause is required for them to search or confiscate anything. They do not always (dont quote me but 95% of the time do) need a warrant to search your belongs if there is Reasonable doubt that you did in fact commit a crime. They do need a warrant to seize property that is not in plain sight assuming there is probable cause to do so. They can temporarily "detain" your kit with reasonable suspicion until probable cause is found, but they cannot turn it on, delete photos, or screw with/delete anything. If you only put in legit nic juice your fine. I would only put wacky tobaccy nic juice in at home.
As was explained to me by my lawyer, if you get cuffed but don't get put in the back of the squad car, be cooperative but dont say anything that could potentially make you look guilty for anouther crime, even as a joke. But if you do get put in the back of the car you can request a lawyer even before your rights are read. He seemed very clear about this after I was arrested for "suspicion of terrorist activity" and learning that I know how to get out of handcuffs and zip ties while doing an assignment on a hotdog vendor here in Harrisburg. .
The police don't know all the laws because there so many of them, but they are always willing to learn, especially with regards to new technology. I'm not a lawyer or a cop and this is based on my own personal experiences. If there are any police officers that can weigh in on this, please correct me.
If you get taken in, lawyer up! There is a big difference between being detained, charged and convicted
I like the buisiness card idea. I alread keep them for my autism and photographers rights, so an ecigarette card would be no problem.