The 2400GE is last generation technology and is discontinued, but you can get the same results using a 2400G and manually underclocking it. The 3700U is a mobile processor so you can't buy it unless you're an OEM like Dell, HP, etc...
Is this CPU widely available now. I like the idea of a 35W CPU but I am wondering what next year's processors will bring to the table for my X570 platform.