GH Rio (Barra, in a suburb along the sea) has a wonderful club lounge with windows and balconies on both sides of the building, so that you get both ocean and lagoon views. Good F&B too, including free drinks at happy hour. I think it's a great hotel, although it's a long taxi ride to most of the tourist attractions. The place has its own beach with lifeguards and attendants who seem to be hotel staff, but I suspect that all beaches in Brazil are legally required to be public access.

I think the Hyatt in São Paulo has a lounge, but I've never stayed there.

As a very general rule, GH should all have lounges, some HRs do and some don't (it's not required at all for the brand), and other brands generally don't have lounges (although some properties in Asia are exceptions).