I have not read Rex's "guide" throughout, just scanned bits of it. From that, it seems to be a fairly general summary of some of the methods, without actually advocating this or that method.
Redchigh mentioned my own 4-part series which I think is about as minimal as one can get with the average-sized planted tank. Others here have followed it and report back that it works, and I obviously follow it in my tanks which you can see in the log under the "Aquariums" tab below my name on the left.
Whatever the method, some aspects should be determined by the intended fish. Substrate, lighting, hardscape (wood, rock, etc) and in some cases plant species. Filter also factors into this, as not all fish need the same degree of current.
You mentioned livebearers with your hard water, so one suggestion would be a tank with a fine gravel substrate in that "natural" brown/tan mix or the darker "Birdseye" mix, with some rounded pebbles of varying sizes to represent river rocks and boulders, a couple chunks of wood. Plants like Vallisneria, plus floating plants. This would represent a Central American stream nicely.
I buy my plants locally, so will have to leave it to others to suggest reliable online sources. Hope this helps. And, welcome to Tropical Fish Keeping forum.