Looking for a good sight for my AK is the krebs AR style a good one? How and where does it mount. Any other options?

It mounts to the very rear of your receiver cover.  The good thing about it is it increases your sight radius but the downside is that if your cover is not perfectly stable or does not position itself the same way when removed and replaced you will have an inaccurate rifle not capable of holding a zero.  I believe Mark Krebs has a solution for this and uses it with his custom rifles but as to what it is I haven't the foggiest.