For high VG, I'd say 13.0w, maybe up to 14.0w - 15.0w if you get lucky, depending on flavor.
It's not dangerous to use it much higher, but it won't take long for those dry hits to ruin your vape and kill your atomizer.
18w using 80% PG was the highest I ever got it.
You could vape it real slow and suck a lot of juice into it, but there's no fun in that.