Time for a little story.
Due to my water supply changing from very hard water to soft, and the pH dropped a little over a point, the crypts melted, and everything else died.
I picked up a larger water change garbage can, 55 gallon. To perform a larger change. Since I had no plants.
Due to the fact that there were no plants to eat up the nitrates, they claimed up before a water change to crazy high levels, so I shifted to two water changes a week instead of one, that the calculator was recommending in the first place.
My tank is just a little over max capacity according to the stocking calculator. I think it is at 104%
But as the new plants are growing and filling the tank the nitrates are dropping down, and I am back to one water change a week, and I think that I might have to start dosing nitrates at the rate that it is dropping.
The tank is a 135 gallon but the substrate is kind of deep, and I am changing out 45 gallons a week.
I think that the calculator might figure out how high nitrates are to give you a recommended water change amount. A heavily planted tank will improve the quality of the water, buy lowering nitrates.
But allowing more fish due to plants, I don't think a hudge change, definitely more percentage points over 100% how Manny, I have no idea. But plants would have an effect on the water change.
But I do believe that the stocking level of the tank has something to do with the fish type, and how much room it needs, not so much as the gallon per inch rule that is pretty much old school.