Z170Extreme4 -> Location of the Intel and ASM SATA

From what I can see in your user manual they all seem to be provided by the chipset but I would recommend using the cluster of ports under the chipset heatsink at the bottom of the board. 

It really shouldn't make much (if any) difference as the ports are all provided by the same controller and you are not using SATA express or M.2 devices. If you plan on adding an M.2 or SATA express drive at some point in the future then look at the user manual and make sure you connect your drives to unshared ports. On your board it seems ports 0 and 1 are shared with SATAe and M.2 respectively. As it is unlikely that you will ever use a SATA express device I would connect the optical drive to port 0 and your SSD and hard disk to ports 2 and 3. That way if you ever add an M.2 drive (prices are pretty reasonable now) you won't have to worry about moving around SATA cables to make it work.