Yes, viscosity and boiling point are two different things. If you use above 10% distilled water you will get a sort of unfortunate watery vape experience that isn't great. I might start with less even like 3 or 5%
I have used vodka in my mixes but kind of halted the practice (same with DW) I am pg sensitive so I was quite close to 90% VG and I vape MTL. So distilled water was helpful in lowering the temp of my vape. I did not get any weird sensations using vodka, it's just that if you use vodka in mix, you will taste it pretty heavily. I occasionally will use Vodka if I think it will be GOOD (and not much at all) but if you use vodka all the time, it ends up becoming flavormix 1 with vodka, flavor 2 plus vodka, flavor mix 17 plus vodka, it just all kind of winds up tasting the same, etc.
good luck with your experiments.
Ana