Using the search function would have answered this question for you. S-OFF is a protective measure to prevent a user from flashing radios or potentially bad ROMs/.zips that could brick the device. S-OFF has nothing to due with under/overclocking a device, never has actually. Root/sudo/su allows you to do these and many other functions, I suggest you search those two terms and read as much as you can before you brick your device. The search function/bars are in the upper right hand corners and google(184.108.40.206;220.127.116.11 just to name a few) to find even more.