You'll probably find many answers to this, some vehemently opposed to others!
My tanks (9 at present) are all well planted and are all overstocked according to the community creator. I've had no problems whatsoever with fish health or water quality.
Plants are undoubtedly capable of using up fish waste products. After all, people kept fish successfully for decades before the modern concept of biological filtration came in, mainly by aiming for a balanced tank in which plants and fish complimented each other. In theory, an adequately filtered tank which is also well planted can hold a higher stocking level than one with few or no plants. Having started with a soil under gravel substrate, my plants were growing pretty well before I added any fish, but there was a real spurt in growth once the fish went in. I used ammonia for cycling, which would have provided plenty of nitrogen, and the soil would have enough of the other nutrients. This leads me to conclude that it was the extra carbon dioxide from the fish that was the main reason for the spurt in plant growth.
Unlike Diana Walstad (I don't always agree with her), who says that biological filtration is not necessary in a densely planted tank, mine are actually over filtered, in most cases by having two smallish filters rather than one oversized one. This gives good filtration without causing too high currents and would be less disastrous if one failed.
I do try to create a mini ecosystem in each tank. As well as plants, I also have snails in every tank plus some other invertebrates which I'll get round to writing about some day. My tanks are not neat underwater "gardens", but a tangle of plants including Java moss and lots of floating Amazon Frogbit with long roots trailing down and, yes, filamentous algae in some cases. My aim is to make something that looks like a natural environment rather than a pretty picture and I believe the fish, which are all fairly small and in shoals, are comfortable in these conditions. Many people will probably scream in horror at my stocking densities, low level water changes, low temperatures (23oC or less and other things, but "the proof of the pudding .................".
I have digressed quite a lot, but I would say that you definitely can stock more densely in a well-planted tank and that your 75% is well below what would be comfortable. I'm sure others will have a contrary view.