2 weeks isn't a lot of time.

But being based in Rio, I would suggest a couple of days there. (Pão de Açucar, O Redentor, The Escada, the Biblioteca). Perhaps a day trip inland to Teresópolis or Petrópolis. South to Angra or north to Buzios.

Salvador is fascinating. The Pelourinho is the old city and is beautiful. Easy Uber to the beach if you are so inclined. The foods there would be moqueca (fish stew), acarajé , or vatapa. Think about a night inland there too. Chapada Diamantina is a national park and absolutely stunning.

Foz do Iguaçu. I wouldn't go to the Argentine side. The Brazilian side is far more stunning. The Foz and the Bird Park (across the street) can be done in a day. Though you might want to get time to do one of the evening meal/shows of the Guarani indians.

São Paulo is my favorite city. Yes. It is a megalopolis. Its metropolitan area is roughly 20 million people. Is it like any other bug city? Yes. But bigger. For example, NYC has roughly 8000 "skyscrapers". São Paulo has 30,000. It has great museums, food, music (especially jazz), and just fun. If you can be there on a Sunday, Avenida Paulista becomes one huge pedestrian fair (Same in Rio for the beach avenues. They close on Sundays too).

Hope this helps.

PS Domestic airfare is cheap and easy!