i am running 4 diy 2liter bottles on my 125gal long and i have roughly 15-20 or more ppm of co2 in my tank i have found that if you use 2 cups of sugar the water turns into alchohol before the sugar is gone and then even if you up the amount of yeast you end up dropping the length the bottle can run. i do 1 cup sugar to 1/4 tsp yeast and a small amount of baking soda per 2 liter. if i switch all 4 bottles out at once i get well over 50+ppm for about 5ish days. so i only switch out 2 of them per week. as far as i know it does not matter about what kind of water i have used distilled, well, city, lake and stream water and no difference. this is yeast we're talking about the take a beating when you make bread with it so i really don't think you need to be gentle. warmer water makes the yeast activate quicker but too hot kills. too cold and it takes forever to activate.
Agreed on the excess us of sugar. Your comment is very thoughtful.
Alcohol is the "end game" of our process. Since the yeast is converting the sugar into alcohol, and the alcohol is going to kill the yeast, then it follows that we only need to provide enough sugar so that the yeast can go kill itself. Any more is a waste of sugar. How little sugar can we add in the formula before we have the yeast culture die of starvation?
As far as using yeast that is designed to handle higher alcohol levels...
These strains of yeast first off more expensive and less convenient to purchase than grocery store bought bread yeast in a jar.
Second they are cultured to not only produce higher levels of alcohol, but to do it more efficiently. Therefor depending on the strain you end up getting to intolerable alcohol levels in the same duration of time as if you used less expensive yeast. Granted you had a more aggressive generation of CO2, but this could be offset by an addition generator providing system redundancy at a much lower cost.