I'd say it could easily go either way based on what I know about G3. As an AA EXP I was given free baggage on several flights last year and that seems to be the same with other AA status members that I've read online, but it's not an official benefit. I also had free seating in the front of the plane after entering my AA number in the reservation. Having said that if you're not an AA elite, I wouldn't expect that same benefit since most other OW airlines maintained their allegiance to LATAM. AA was essentially kicked out by DL and had to find a new partner.

Baggage allowance is supposed to be based on the ticket, not the individual policies of the carrier for the segment. However I've had mixed results with that and have had to go back seeking compensation and / or chargeback before for the charges when they were against the stated allowance on the ticket. If your e-ticket shows baggage allowance on it, and G3 charges you then just file a chargeback on your credit card when you get home with the e-ticket as evidence.