Fallout 4 - Yes, pretty sure.
GTA V - No, lack of Vram and power. I have a 770 and can only run it on high. Tbh you probably won't notice a difference between high and ultra anyway.
I'm not entirely sure about it running Fallout 4 and GTA V on ultra but it should be able to push high on both. If you're using an ENB for both then your FPS will be a lot lower.
Fallout 4 - Yes, pretty sure.
GTA V - No, lack of Vram and power. I have a 770 and can only run it on high. Tbh you probably won't notice a difference between high and ultra anyway.