I'm not sure. I vape 6mg these days, but at 2-3 times the power of when I was using 18mg.
What you need to try and get a feel for is can you tolerate more power (in which case, go for it!) or is that as bad as using higher nicotine.
I think the harshness is more in the nicotine than the PG, but other people don't agree.
Have you tried
vaping someone else's set-up? If you tried 12mg or even 18mg on a lower-power device, how would that be.
Your device vapes at 14 watts, but I couldn't deal with 14 watts for nearly 2 years.

In a way, I wonder if you would be better
vaping higher nicotine at lower power, but as I hope I'm explaining, (badly)... you need to work out if it's vapor or nicotine that's the real problem. For me, it was the level of vapor.
My missus cannot tolerate vaping enough to do it more than in emergency. She uses 24mg at low power. She can't vape any of my 6mg at 15/20/25 watts.