Appropriate DDR-4 Memory

[RhoXS]

I am upgrading my hardware and will use an ASRock Z170 Extreme 4 (maybe a 6 ) and an i7-6700K. I will almost certainly overclock the CPU but not to an extreme as reliability/stability are of primary importance to me. What would be an appropriate memory timing spec for this combination? I am looking at either a DDR4-3000 or 3200 of 2 X 8 GB but really do not have the insight to know if either of these is optimum. I am also leaning towards the G.Skill Ripjaws V series.