Ph does play a role at some point. For instance breeding. Some fish are real finicky about breeding waters. For me any spec I see in on a fish profile, I try to meet them as best I can. I don't like taking a fish out of its preferred range. Its better to get fish that are already in the range in which your parameters already meet. Problem is, choices thin out.
I make my water fit my fish instead of making my fish fit my water. With the right recipe of R/O and tap, you get consistent at it. On municipal water, you have no control over what's put in the water. There is control somewhat by the use of R/O water. Dail in what you want with the ratio of tap to R/O. True its easier to allow them to adjust to your water but for me unless they are naturally high ph fish, I don't do it. But that's just me. Everyone will have their ways and stick to them. I honestly fell that prolonged parameters outside of the preferred shortens a fish life span.
I have fish live longer when my waters are neutral than I do when I don't change my water parameters. Look at it this way. A ph of 6.0 is 10x more acidic than a ph of 7.0. A ph of 8.0 is 10x more alkaline than a ph of 7.0. But a ph of 6.0 to 8.0 is 100x more acidic/alkaline when skipping a ph 7.0