Perhaps I am showing my ignorance but... Laptop came with a 128GB SATA 3 M.2 2280 SSD and a i5 7200u cpu. Did this model come with different motherboards dependent on the SSD &/or CPU installed? I would like to up grade my SSD to a 512GB or 1TB but do not want to buy a SSD faster than the motherboard has the ability to fully utilize. I understand a faster SSD would probably be backward compatible but why pay for speed that will never be utilized.? Will it accept B&M key or just M key m.2 2280 SSD's?