It will also be minimum of Nvidia 960, so your machine is well below minimum requirements.
Also we can't tell you how long it will take to load between levels because:
1) There is no standalone exporting in any of the alphas yet.
2) It all depends on your machine, so if we don't have the exact same machine as you, we don't know.
Primary Desktop:
i7 7700,k NV1070 8GB, 16GB 3200mhz memory, 1x 2TB Hybrid, Win10.
Secondary Desktop:
i5 4760k, NV960 2GB, 16GB 2333mhz memory, 1x 2TB Hybrid, Win10.
Primary Laptop:
i5, NV1050 4GB, 8GB memory, 1x 1TB HDD, Win10.
Secondary Laptop:
i3, Intel 4000 series graphics, 6GB memory, 1x 500gb HDD, Win8.1.
