The simplest way to ensure the most stable water conditions is to make large, frequent water changes. Aerate and warm your water for 24 hours before the water change to avoid pH shifts. Your comment on setting up the easiest and most efficient water changing system is critical to success in this hobby. If you do this, the water in your tank never gets dirty. Your reservoir becomes the entire water table of your locality. It does not get any more stable than that.

As you have surmised, the actual water readings are less important than stability. Discus cannot live in constantly changing water conditions (neither can any fish), so that's why you see constant references to clean water in bare bottom tanks. Most of us start with elaborate water testing. Then we stop because the readings never change with constant water changes.

Have fun, Willie