Who on earth came up with the idea that a heavily planted tank requires a filter that changes the water at least 10 times an hour? It seems totally absurd. First of all, I very much doubt if most plants would thrive, or even survive, in the speed of flow that would cause. Virtually all aquarium plants come from still or very slow waters, indeed most of the commoner ones are actually marsh plants rather than true aquatics. Second, it is clearly assuming that the filter bacteria are entirely responsible for dealing with fish ammonia, whereas one of the major reasons for having a densely planted tank is that the plants will do a large part of that work. On this basis, filtration can be reduced in a well-planted tank rather than increased. I suspect that this idea arise from some concept of "dead spots" where the water doesn't circulate because of the dense planting. While this might possibly occur in a very large tank, I don't think it at all likely in any domestic size aquarium. I've had a good look in all the corners of my tanks, which have "normal" levels of filtration, and I can see water movement everywhere. In any case, as noted above, the plants will deal with any ammonia or whatever. Even with no water movement at all, anything in the water will spread surprisingly quickly by diffusion alone. I think the idea of dead spots is one of those greatly exaggerated remote possibilities. If you are still worried, two smaller filters, one at each end of the tank, would probably be a better bet than one big one.
I also think that too much filtration can be a bad thing in that it is generally results in increased flow rates through the tank. Three of the used tanks I bought came with oversized filters. In each case, when I tried running these in those tanks the amount of water movement was ridiculous, far more than most fish would find comfortable, while the plants were flapping around like palm trees in a hurricane. There are many videos of people's tanks on YouTube etc., where one can see small fish (usually tetras) being subject to constant buffeting by a current which is far stronger than they like, subjecting them to continuous stress. I don't think many fish would be happy with a filter rate of 10 times per hour. More is not always better.
As far as stocking levels are concerned, if your tank is working OK then it is not overstocked, whatever any guide might say. This means regular water testing, but also observing your fish to make sure they are getting on. There's more to stocking than ammonia and filters. You could have two small fish in a big tank, but if one is making the other's life a misery by constantly chasing it, it could be argued that the tank is overstocked by one fish. Conversely, if you have only one or two of a type of fish which should really be in a shoal of six or more, then it might be said that you are understocked.