Well, I get mine pre-mixed from Cignot.com.
However, if I thought I was sufferering from PG I'd probably get a bottle of PG and a bottle of VG. I wouldn't mix up a large batch or nothing...one cartridge would do.
Take a dry, empty, cartridge. Put PG in it. Vape three or four drags...then go back to your usual
juice with a different cartridge--wait and see what happens.
Hmmm, maybe I misread your post.
YES, you can
buy PG and VG seperate--you don't 'have' to mix them. Juices are sold with both or just one in them....and they both are sold seperate.
So all in all, you can do it the way you want to. You can buy PG...you can buy VG...you can buy a mix of both...you can buy flavor that has neither and add your own...etc.