You are right, I know about these 2 variants, but as I said - 2gb 860m (which i am considering) should be maxwell. The 4gb version of this card can be kepler. Look here: http://wccftech.com/nvidia-geforce-gtx-860m-features-maxwell-gm107-core-45w-tdp-benchmarks-unveiled/
And, basically, we can...