I had a 1060GTX 6g EVGA Mini , I could barely do teamfight, as soon I had around 20-30 player fighting, my FPS was going around 15-25FPS ( This is before Performance Patch tho).
I have a old CPU 4790 i7
I switch for a EVGA 1660Ti and its like Day and night. I have 144FPS and probably around 40-80 in teamfights at minimum graphics.
When i look at the specs they have the same but the performance difference is quite crazy.
go for a 1660(normal size) or 1660Ti. The Ti one u wont regret it (depending on the price) if you still play in 1080p.