Officially Apple uses Gen 4th SSDs for MacAir(late 2015) and for Pro they used NVMe enabled SSD wit PCIe 3.0 comm tech. But, now they use the Gen 5 NVMe SSDs with PCIe 3.0*4 channels. Speed is quite far-reaching, and for your requirement, I would go with 500GB for the OS and 1TB for the rest of...