Considering that you're going to be using a 7700k I would guess you'll want a Z270 (Overclockable) chipset. This (http://pcpartpicker.com/product/7VZ2FT/asus-prime-z270-a-atx-lga1151-motherboard-prime-z270-a) is a popular choice however I would encourage that you browse around on pcpartpicker.com with the Z270 chipset filter enabled. As for M.2, it will result in higher speeds if you get a SSD to support those speeds. M.2 is simply the plug, what determines the speed is the protocol that a drive uses.