Generally, doctoring the water requires understanding of buffering capacity & accurate measurements of your water parameters ... pH
KH GH, etc.
There really is no "auto adjustment powder" you can use. Most of these products just change the pH temporarily. <Because they don't contain enough buffers to overwhelm your native buffering system in your tap.> You end up with yo-yo-ing pH which is far more stressful to the fish. Better to stick with a stable pH. <And 7.5 -8 is not that high for your fish!>
As to ammonia, it is true that ammonia is more toxic at higher pH .... but the treatment is to remove the ammonia, not mess with the water. <A fully cycle tank should have no measurable ammonia anyhow...>