Tap all day baby. Chlorine is overall beneficial. Mild disinfectant and it is a often forgotten plant nutrient needed in small amounts.
Unless, of course, you truly live in a place with truly awful water. My water is very hard, and I do fine. Medium-hard is best, some alkalinity and dissolved minerals are generally helpful. 95%+ chance you live somewhere with acceptable water.
What’s your tapwater pH after you let it sit out a few hours? Letting it sit out a bit lets you get a more accurate pH.
If you already have an R/O unit, I’d use it, but then you have to add minerals for optimum nutrition. Always a million ways to skin a cat, I just prefer tapwater.