There's 1 resort in the actual national park that just opened a few years ago - the Gran Melia. Not to be confused with the resort area, If you look on a map where the Hilton is - that's the resort area, it's a circular road & there's probably 10 or 15, 4 & 5 star hotels on the road and various luxury villas in between. Both Gran Melia & resort area are heavily patrolled, stay here if you can. Many good restaurants, lounges, etc.
Right south of the resort area, across the highway is the "nice" area of Iguazu, it's a residential area that's mostly safe because everyone has tall walls, barbed wire, electric fence & won't hesitate to lynch. If you can't swing 100-150 us p/night in the resort area or 250 for gran melia, try to stay here, lots of nice cabanas for ~50 p/night. A taxi that won't rob you will cost about 10 usd to go into the town from here.
The actual town of Iguazu is mostly smugglers, Brazilian gangsters, poverty, etc. I don't go there. Most people will tell you Iguazu is very safe as long as you don't do something stupid like make eye contact with someone, use a phone/laptop/etc in public, need police services, so ymmv.
PS - When traveling around Argentina, all the upscale stuff in Argentina is generally legit, tax paying businesses that follow the rules. If you pay with a foreign card they'll give you 20% discount & the majority will accept cash usd around the blue rate. I can confirm this works.