Yes, now in Brazil you can hardly find anyone not using Pix. It is all digital and free. Even in Argentina and Paraguay, many local merchants are now accepting Pix.
Yeah, in Argentina the main digital wallet is MercadoPago. Many merchants have their terminal to accept payments with credit cards/QR, and since this past summer you have the option to accept payments with Pix too.
Also it goes both ways, everyone going on vacation to Brazil can pay with MercadoPago without having to install Pix.