Any hotel will arrange a tour, but the Argentinian side, like the Brazilian side, is very straight forward and you don't need it. One boardwalk along the Brazilian side - easy. I took a hotel tour (actually just a driver) from the Brazilian side to the Argentine side because I was flying out later that day and I wanted someone to keep my luggage safe, and also to take me to the Sheraton on the Argentine side, so I could shower and change before my flight
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When I went there, Argentine park admittance was CASH ONLY. There is an ATM at the entrance, but I was told usually broken, and it was on the day I went. When you get in, there is a little train that takes you from the park entrance to a couple of stops along the extensive Argentine falls. From each stop, you can walk along good metal boardwalks along the brow of the various falls. One track descends to the river level where you can take boat trips. I didn't do these. When I was there, there was a plan to connect them all the walk segments up, but back then you had to take several segments on the little train. The final stop is for the Devils Throat; there is about 1km of metal boardwalk out across the river and little islands, till you are right above the major part of the falls.
On the Brazil side, make sure you go upstream beyond the high tower and visitors centre. You can take boat trips on the river upstream of the falls
. Don't undervalue the time needed on the Brazil side - the best pano views are from that side.
Watch out for the racoon-like animals on both sides - quite aggressive for food (even when carried in bags) and act like big rats.
Tip for IGR. One you go into the departure lounge, there are virtually no amenities. I joined a queue an hour before the flight, but that was a mistake. Having OW 'Preferente' was a God-send; 1 pax priority boarding (me) and a scrum of over 100 other pax, following.