After googling, I found that GTX 970 is better than GTX 1050ti, what I noticed is the DX version. GTX 970 is DX 11 and GTX 1050ti is DX 12. If I buy GTX 970, does one down DX version than GTX 1050ti will matter?
Both Cards support DX12,the GTX 970 outperforms the 1050ti and in order to use DX12 you need DX12 games.
Games that Can use DX12 can be found in this wikipedia list:https://en.wikipedia.org/wiki/List_of_games_with_DirectX_12_support
You will also need Windows 10 to use DX12