Will a sli 770 2gb be good for modern day games? It performs fine but sometimes it's slacking in games like pubg, or should I wait till gpus stabilize in price and get gtx 1060?
The first issue here is that that VRAM is not additive during an SLI, that is you will be staying at 2GB, it does not add up to 4GB. This compares to either 3GB or more likely 6GB for the 1060. PUBG will be affected by only 2GB of VRAM.
For performance comparison it becomes a little more difficult to assess as it is very game, settings and GPU model specific. I have seen reported performance improvements for two SLI'ed GPU's range from...
The first issue here is that that VRAM is not additive during an SLI, that is you will be staying at 2GB, it does not add up to 4GB. This compares to either 3GB or more likely 6GB for the 1060. PUBG will be affected by only 2GB of VRAM.
For performance comparison it becomes a little more difficult to assess as it is very game, settings and GPU model specific. I have seen reported performance improvements for two SLI'ed GPU's range from about 2% to 98%. A reasonable expected improvement will be around 80% on average. https://videocardz.com/42112/official-nvidia-geforce-gtx-770-performance
If you assume 80% scaling that would mean the two SLI'ed GTX 770's would be a little stronger than the GTX 1060 but not by much. And I believe this analysis would break down as you have the 2GB version.
So my recommendation is to wait for the 1060, a lot less headaches and there is a reasonable chance that GPU prices will be coming down in the next few months (no guarantee).