I usually use VG nicotine and PG flavors, and count them as part of the PG/VG mix. I use 100mg nicotine in VG, at 10% to get 10mg of nic in my liquid, and count that as 10% of the VG. If I use, say, 10% TFA flavor in PG, then that counts as 10% of the PG.
Acute Sinus allergies will not let me
vape above 30% PG. Any more than that causes allergy irritation. so I have to keep a close eye on my percentages. I still use up to 30% PG as I find the flavor better, and strait VG just seems a little too much vapor.
So I guess I am mixing to my 'happy medium'.