X is unlikely to be Plutarque, for https://www.napoleon.org/wp-content/thumbnails/uploads/2009/... (depicting him at 15) was supposedly made with some input from the principal himself, and the book is supposed to be the Lives (also frequently mentioned by others in a cursory search).

Between Cicéron and Tite-Live my priors are (0,5:0,5) because it seems like he read whatever he could get his paws on: https://blog.napoleon-cologne.fr/napoleon-bonaparte-et-les-l... (with a rather Molochian /dev/null for books not worth the time to read? War and Peace also mentions french book burning habits, but those were driven by more prosaic motivations)

EDIT: > "it is an advantage if from time to time there are individuals who do not understand men" —???

(which reminds me, I still haven't tracked down one of your earlier paraphrases...)