Its a good graphics card for the price. Temperatures are ok. While running unigen heven this card touched 82 degrees, however, while playing games like GTA V, Witcher 3, etc on 1080p 60 fps settings mostly high to ultra temperatures never went beyond 65 degrees.
But when it is in load fan gets loud, that could be due to the small heat sink, which is quite small then there should be.
I had an AMD card earlier and I am not a fanboy of NVIDIA. However, at the price point of 15999, I would take GTX 1660 over RX 580 any day. 6GB of VRAM on GTX 1660 is 2GB less then RX 580 but till now I have not faced any problem because of that, for current titles, I think GTX 1660 is the best bet.
Bad thermals due to crappy heatsink design. Don't be fooled by dual fans! One of the fans just blows over the PCB while the other blows over a small heatsink. Temps reached 88-91°C+ in just 2 minutes. Even after tweaking the fan curves in afterburner the temps merely come down by 5°C and still throttling in most titles. Spend a little more and but a card with proper heat pipes.