Brazil – any recommendations; payments

Brazil is very forwards when it comes to non-cash payments, and debit/credit cards are very widely accepted. The FX rate you’ll get on any int’l card is very reasonable (of course best to use an FX fee-free card).
I very rarely every had a reason to use cash in Brazil. The exception may indeed be street vendors (some do accept cards though). PIX has grown to be a very popular payment method but don’t think you will be able to use it unless you have a Brazilian bank account.
Try withdrawing cash from bank own ATMs (not the multi-bank ones that charge a fee – annoyingly that’s the only kind when you land in GRU for example).

The classics in Brazil (and as someone stated, the country is massive, so you will need to take into consideration)
1. Rio and surroundings: I’d stay 3-4 nights in the city (base yourself in Ipanema or Leblon, Copa is a bit dodgy at night), and then head out to either Buzios or Ilha Grande.
2. Iguazu falls (can easily be done in 2 days/1 night: fly to Iguazu, the brazilian side of the park is next to the airport and can be done relatively quickly. Find transport across the border to Argentina, overnight and head to the Argentinian side of the park which takes a bit more time. Return across the border and fly out again – or alternatively continue to Buenos Aires from the airport on the argentinian side)
3. Salvador: colonial town in the heart of Bahia. Churches, Beaches, Northeastern culture
4. Brasilia: bit niche, but really enjoyed the 50s/60s architecture and interior design (2 days/1 night) found there.
5. Lancois Maranhenses (dune system with hundreds of fresh water lakes. visit in June-August after the wet season) Unique and impressive, but hard to get to.
6. Jeri and surroundings: has developped quite a bit in recent years, but still enjoyable especially if you have interest in kite surfing (windy season is I think July – but I’d double check).

Enjoy!

Good luck!