Unless you are adding a PG based flavor concentrate you will remain at the same ratio. Mixing premade juices that have the same profiles only combines the flavor profiles. It would be no different than dripping more juice onto your coils in your RDA it doesn't increase your nicotine PG or VG it merely makes the wick more saturated with liquid. Now if you mixed 20/80 with 30/70 then you might end up with 25/75 as it would split the extra 10% of PG. And the only way your nicotine will increase is if you were to mix equal parts of say 6mg with 9mg then you will end up with like 7.5 MG juice as it will split the difference of the 3% increase in nicotine. Hope this helped