There may be your answer then, up until 10056 all W10 builds were working better than 8.1 but then with 10061 everything got worse. And I use 1GB of pagefile for compatibility reasons. DX12 driver means it's a different driver batch than this one, not that the game has DX12. And I have 100% GPU usage even FPS drops so that's still the limiting factor, or the driver. Seemed like W10 kept trying to flush the video memory. Also noticed a difference in the beginning at the loading story mode, in W8.1 the VRAM increases gradually until 1.2GB whereas with the W10 driver it kept staying below 400MB, like there was a hard limit.