Is there a difference in pronunciation or mouth movement in the assimilation (idgham) of the non-vocalized noon (nūn as-sākinah) and tanween with noon and meem, between considering it a complete assimilation (idgham kamil) with ghunnah into the assimilated letter, or an incomplete assimilation (idgham naqis) with ghunnah for the assimilated letter?

The assimilation (Idgham) of nun sakinah and tanween into the letters nun and meem is an assimilation with ghunnah (nasal sound) that is incomplete in its emphasis (naqis al-tashdeed), not a complete assimilation. The majority opinion is that the ghunnah when assimilating them into the meem is the ghunnah of the meem, not the ghunnah of the nun sakinah and tanween, because they transform into the sound of the meem. As for what has been narrated by some concerning the assimilation of the ghunnah and its removal when with the meem, that is incorrect.