Using PGA or vodka is a balance between thinning and TH, and vapor. Hard to say what %s correspond to this subjective terms, but I have used it at 5% in my VG DIYs, with good results on TH and flavor blooming. Had to stop using it though, as it dried me out too much. How much you can use and still have vapor depends if you are
vaping PG juices or VG juices or some mix. It will thin juices about twice as well as water does, so it doesn't take a lot to kill vapor. If its a PG
juice, maybe start with 2% and see what happens. TH also depends on amount of PG, the flavor, nic level and how thin the
juice is. Play around, keep track of relative amounts of components, and let us know what you find out!