I'm almost 200 hours into a second playthrough of Fallout 4. My 980 Ti still maxes it at 1440p 60 FPS even with the high res texture pack. I get the same occasional frame drops as I did the first time I played in certain areas especially Far Harbor ( the fog ) but the high res texture pack didn't hurt performance at all that I can tell. A 1070 shouldn't have any problem.
Please imagine for a moment how my GTX 1050 Ti chugs in Far Harbor with the high res pack. Well, at least the little thing overclocks 200Mhz easy...
Anyone want to donate a 980 to the cause? j/k