BS”D
Wolf: What exacly Niv’im are is also subject to a machlokes Rishonim, whether they are the words of the Navi’s understanding of the nevuah or the word of Hashem telling the navi what to write.
The practical Nafka mina is if reading navi without understanding it is a mitzva of Limud Torah (as Torah is, since it is the direct word of Hashem).
Navi was NOT given at Har Sinai, and if fact the Gemorah explicitly states (I think also in BB) that if not for the jews sinning, there would be no Navi other then parts of Yehoshua dealing with how the land was divided.
Ben Levi is correct regarding the Machlokes. Interestingly, one of the Rayos that the Torah was not given with all the words at Har Sinai are the paradoxes created by the Miraglim and Maase Mire’va, and why they would have been attempted by Moshe if he already knew the result from Hashem. (thought Wolf would like that one).