Any CPU heavy title, the 7400 will hold back a 1080. I have not played AC origins, but for BF1 it will definitely hold you back. BF1 has the 6600k as the minimum CPU requirement, and the 7400 is below it. So there will be some stuttering with a weaker CPU but you should have reasonable fps.
My belief is to build a system around a GPU. So I would go get the 1080 and have the plan to upgrade to a 7700 later. You can get a 7700 at microcenter for around 250 and it will have no issues pushing a 1080. But I would not get a 7700 now and pair with a 1050, because you will have too much CPU and not enough GPU.