You can stock a "FEW" more fishes, but you still cannot go over-board. I have about 90 fishes in my 100gal (and it is very heavily planted) but most are tetras.
Well, the thing is, is the biofilter in a heavily planted tank better? Yes
In general, does a better biofilter mean the tank can handle more fish? Yes, in general.
However, in a heavily planted tank, I think you'll find there is physically less room for fish, so you'll likely end up with less fish to keep it from looking over crowded.