Does saying "Insha'Allah" silently in one's heart differ from saying it aloud?

If the meaning of "Insha'Allah secretly in the heart" is to conceal it without moving the tongue, then this is not sufficient and is not considered speech. However, if the meaning is to pronounce it with the tongue in a voice that one cannot hear oneself, then this is sufficient only according to the Maliki school, but not sufficient according to the majority of scholars (Hanafis, Shafi'is, and Hanbalis) who stipulate that the speaker must hear themselves. And whispering in a way that one can hear oneself is sufficient. It is recommended to link the will of Allah to future actions in compliance with His saying: "And never say of anything, 'Indeed, I will do that tomorrow,' except [add], 'If Allah wills.'"