Not much point trying an i5 or an i7 as the chipset doesn't support overclocking.
Might make a decent crunching rig though.
Not sure about that. If you look at this gigabytes manual, you can see that there is normal OC tab where you can change cpu clock ratios. But yeah you are right chipset does not support OC, so there might be an error in manual(might be just copy paste from some z170 board, at least theres no F2a bios for x170 board).