hello
there is no crossing from Argentina to Paraguay, it goes from arg, (ruta 12) to brazil than (ruta 277) to ciudad del este.
on weekdays there is hardly any wait on the friendship bridge (brazil/paraguay) so you most likely just cross in and out without any one checking documents. but on weekends it is a crazy wait so people go to by fake goods
so if the issue is renewing your visa, it will be based on arg/brazil crossing, which you do need a visa to enter brazil. now i heard that brazil does provide temporary visa if you are just going to the Brazilian side of the falls, but i could not confirm this since i was good to enter brazil with my passport.
my understanding is that paid border/land crossing visas are required for all border countries, excluding Uruguay and chile
hope this helps steve