[@Gareth] Everything in the CS will be publicly known things, and those things which are necessary for the reader to actually understand your character. So their power level is really up to you, as to whether you want to make it known to the public or not. If you post it on your CS, cool, it'll make things easier on the rest of us, but if you'd rather make it known in the IC over time, just let me know in a PM and we'll sort out the details.

A good way to figure out your power level is by checking one of the guides online, which details the power levels of canon characters (such as this one: http://www.tor.com/2015/10/27/the-wheel-of-time-companion-strength-chart-of-major-channelers/), then use that to determine your character's strength. Consider the fates, the trials, and weaknesses, of the characters who hold the most potential in the One Power, too. 

As mentioned in the introductory post, if your character is immensely powerful, they must have equivalent weaknesses; like a woman who is an incredible Aes Sedai, on the same level as Lanfear, might have debilitating PTSD, a lame leg, and a child that they would sacrifice everything to save. So really, the amount of power you want to give your character is up to you- just know that the more OP they are, the riskier that is.