As for RAM stated speed...look at the motherboard documentation. If the motherboard supports 1600 as an overclocked speed...and you want to overclock...then it's a consideration. If you have no intent of overclocking, there's no point in purchasing RAM designed to run at overclocked speeds...and the motherboard may possibly balk at running the unspecified RAM if the board doesn't support the higher spec.
Quite honestly...overclocking systems was a typical way of getting more out of a system...when I bought my first computer in 1996. With today's technology, the value of overclocking a given system...is probably not going to produce the results it may have 15 or more years ago and overclocking brings risks that I consider to be totally unnecessary for today's processors and systems.
My impression (nothing more than that) is that the same persons who overclock...do so because they are in the same mindframe as those persons who customize their autos for questionable speed stats. It's just an individual fooling with his/her system...because he/she can and wants to. Nothing magical about or necessarily mandating it.
Worth A Read, IMO