speaking from personal experience:
I find that the higher the nicotine level and amount being vaped can significantly increase anxiety and increase heart rate... vaping too much nicotine can very possibly have you jumping out of your skin... be careful...
I started with 24mg to help me quit smoking but reduced mine to 18mg after a couple of months and now I vape that all day everyday. I was a 1 to 2 ppd smoker for 37years so it's not like I'm going to just stop completely or drop down to a lower level bc I'm worried about the nicotine. The higher levels did give me headaches but now that I'm at 18mg I don't have a problem. When I'm ready to reduce to a lower level I will, but I'm not heading there right away.