You're options are almost endless, because the Amazon is really thousands of streams, and rivers feeding into one, with as many different habitats. It might be determined by the species to be kept.
White water, black water, clear stream, oxbow, and it goes on and on.
In one for small fish, the entire substrate might be covered in leaf litter, in certain Geophagine biotopes there might be no plants, just large expanses of sandy areas with lots of sunken wood, in the oxbow type, terrestrial and aquatic plants, another a fast flowing stream with gravel for Retroculus and other rheophilic fish, etc etc.
Below a S American moderate flowing river, habitat where you might find Geophagines. I took many photos under water to see what the bottom looked like. Above the waters surface plant life was quite lush, yet almost a desert below.

To mimic it in my tank I did this

Above I added tannins with every water change, but not to the extent of
my current black water river tank below.

In some of the oxbow pools leaf litter on the substrate was 6 " thick, and the only vegetation terrestrial.

In my tanks I like aquatic vegetation, not only for looks, but its ability to eat/use nitrate, so even though in much of the habitat I saw was devoid of plants, I use aquatic and terrestrials anyway.
