I don't know anything about BGK but angels can mix with a wide range of other South American cichlids. I've kept angels in almost every tank I've had over the years with tankmates that include: severums, festivums, chocolate cichlids, keyhole cichlids, flag cichlids (Laetacara sp.), Uaru, discus, rams, Geophagus parnaibe... they do well with a lot of things.
My only suggestion would be to avoid the festivums. I've had three groups now and they're all aggressive. They dart at and attack other fish that get too close during feeding time. My angels have suffered split fins from this.