You won't be able to handle more than low, to medium, in either of those games. ACU is horribly coded, and even high end rigs can struggle with it. I have an i5 3570k @ 4.0ghz, with a GTX 770, and would have to play on low, to keep the minimum FPS up enough to make it playable.
Witcher 3 is better, but still quite demanding.