With regular inert substrate and active growing-thriving stem plants that cover at least 75% of the floor and that need trimming at least every 7-10 days-that is moderate stocked-including shrimp and common snails along with a Betta...
Water changes of 25-50% every week or two, however, if you are adding any ferts to the water column-It is best to make at least 25% water only before you add ferts to remove any unused ferts so the algae can't use it.
While some specie of algae is normal, expected and can be a sign of a healthy system-its still a closed system. Maintaining the balance can help keep the algae controlled to a degree along with regular manual removal.
One of the best plant ferts is fish food by the way-leaving any uneaten will be used by the plants. Plus you have natural decomp that will happen and this will help to produce natural CO2 for the plants-With that natural CO2-depending on the amount can also reduce the pH naturally.
A lot of different things can happen in a tank full of plants and so many things can vary too-Some things you have to kinda play-by-ear....so-to-speak.....The more mature the tank-the more complete the ecosystem with everything working together, however, we have to remember that its still a closed system and we have to be mother nature.....Water change is our main job......When you have a mass amount of thriving plants even with inert substrate-you don't need or want to vacuum too much or too deep-but you do need to swish up the mulm/debris on the substrate on occasion and suck it out- so you don't have too much of a build up since the inert substrate can't eat/use it like live soil will.
Active growing live plants will benefit the system-the key being active growth-if you don't have active growth the plants can end up being the cause of water quality issue. Most plant failures are due to incorrect color temp lights, too short a photoperiod, incorrect planting and poor nutrition to name the most common causes of plant failures. Not mentioning the non-aquatic plants that are often sold as aquatic
Can you tell us more-type of substrate planned and how deep, filter, number and species of plants, final stocking, additives planned and lights-age of bulb, watts and kelvin and we can give you a better idea on water change needs.....If you already have it setup-can you post a pic....