I was recently in a pub which had water bottles from the different regions of Scotland, so you could add drops of the same water it was made from.

Also, a pipette to exactly measure the amount of water added. It was excellent.

Yes, a few drops, and I mean drops, of water can change the flavors of the whisk(e)y. It really doesn't matter to me. Depending on the water you might use can matter also. "Branch water" is historically the water used by bourbon drinkers. Branch water refers to using the same water that was used to make the bourbon to add to your glass. I have no idea if it matters or not. But that's folktale.

Adding ice can do the same thing along with dulling flavors due to the chilling of the bourbon, except melting ice is not under control. It goes from perfect to just a bad glass of water as it melts over time.