Does the words you choose for your poems change anything?
In the poem building minigames, you pick words to form your poem.
Do they change anything in the game, or is the game completely on rails and the poems you create dont matter?
The words you pick will directly give you points to a specific girl, related to the word/her attitude. Source.
Each word will give a number of points to a specific girl, and at the end of the 20 words whichever girl has the most points will end up being the "favored" one for the next day (meaning in the first two days of the game's plot, you'll get their CG scene for that day).
Emphasis mine.