What is the difference in the ghunnah of ikhfaa’, substantiating your statement with Quranic examples?

The ghunnah (nasalization) follows the letter that comes after it with ikhfaa' (concealment). If the letter is from the letters of istilaa' (elevation), the ghunnah is made heavy (mufakhkhamah). If it is not, it is made light (muraqqaqah). It should emerge smoothly without elongation or excessive movement of the tongue, and its duration is two counts.