Actually boiling water boils off some of the chemicals while concentrating others...and concentrates the minerals. Distilled water is best (although we've used Reverse Osmosis filtered for a few small batches). For a small batch, it's likely okay to use the filtered water (as long as the minerals and bad tasting chemicals are filtered out adequately).
While we can add a very small percentage of alcohol to our vapes, please do not substitute 20% - that much vaporized alcohol is NOT a good thing.
We make a "VG Base" that we use for all of our mixes; it is 80% VG; 13.5% distilled water; 4.5% saline solution (.9%) and 2% pure grain alcohol (we used to use 9% dw and 9% saline, but when we changed wicking material to Nextel the
salt flavor came through, so we lowered it).
When mixing, we plug that Base into our calculators as plain VG.
Happy mixin'!