A video about chinese 1660 GTX with 6 pin connectors, also comparing it with the 8 pin version
Here are some links in TechPowerUp:
https://www.techpowerup.com/gpu-specs/kurotoshikou-gtx-1660-oc.b6840
https://www.techpowerup.com/gpu-specs/galax-gtx-1660.b6838
https://www.techpowerup.com/gpu-specs/gainward-gtx-1660-chasing-wind.b6832
https://www.techpowerup.com/gpu-specs/galax-gtx-1660-general.b6839
https://www.techpowerup.com/gpu-specs/gainward-gtx-1660-glare-oc.b6833