Performance of a Graphics Card on mini-PCIe?

[Doctrsonic1]

If I were to get a mini-PCIe to PCIe 16x adapter and run a graphics card off of it, what kind of performance should I expect? I recently upgraded to a GTX 1070 and have my GTX 960 sitting in an unused computer and was wondering if it would be worth getting a cheap adapter. I have several old laptops, some of which have broken screens. Would an adapter for my graphics card work, and if so, what kind of performance in game should I expect?