(If you are American) Would you suggest someone fly from NYC to Las Vegas to spend a couple of hours looking over the rim of the Grand Canyon and return same day? Same with this Manaus plan you are insisting on.

Raffia is not referring to Tours by Locals, which btw is simply an advertising site for those looking to make money as guides and who may not have official city credentials and are not vetted in any way by the site as long as they pay up. He is referring to a number of "favela tours", mostly in the Rocinha community, who drive through the slum in the manner of people at the zoo looking at the animals. These days, if you wish to get up close and personal mostly in some of the poor neighborhoods on the hills behind the main beach neighborhoods, there are tours led by people who actually live in the neighborhood, like the one he mentions in Santa Marta. Or the Rocinha tour with Zezinho.

You need three days/two nights to devote to the falls to make the trip worthwhile , but the first morning is used to fly in and the last afternoon to fly out. In that time you can walk the path on the Brazilian side, taking photos, see the Bird Park near the Brazilian park entrance, do a boat trip on one side or the other, get back and forth across the border and walk the main trails in the Argentine park, with some time to enjoy the shade by the river and the coatis.