Hi,
In rheumatic fever, the antibodies generated against streptococcal antigens cross react with many target tissues in the body resulting in molecular mimicry. So damages result from cellular interaction between antigen and antibody and it is regarded as type II H/S(cytotoxic).
In PSGN, the circulating immune complexes in the serum resulting from streptococcal infection become deposited in the kidney. Damages are due to the immune complexes and it is regarded as type III H/S(immune complex).