VG - breaks down into Glucose in your system. This can throw sugar levels out of whack so you need to be careful and monitor your levels, if you see them rising or slipping I'd switch to PG.
PG - breaks down into Lactic Acid. This is one of the reasons it drys out the throat, irritating it, and can make you feel slightly achy the next day as if you had worked out.
Now with those issues out of the way, vaping, if continuously is still putting an irritating foreign material (vapor) into your throat on a consistent basis, you'll find the coughing stops coming from the lungs like with smoking, but instead issues from the throat.
You can try VG and that should help some, and then drink water when you vape to keep your throat moist. Other than that, eventually your body should become accustomed to the vaping like it did with smoking.