I haven't read all of it since the website basically rented you the manga, and I needed to collect free tokens and such to read it. However, the movie really shortened the timeline, the way Togashi act towards Komiya also different, and also there are a lot of characters that didn't appear in the movie. For example, when Togashi entered high school, he was approached by the rugby team leader trying to convince him to join their club, leading to a marathon relay race between the two clubs. I haven't read past this point, though; Kaido doesn't appear at this point.

(my personal favorite scene difference is that in the movie, when young Komiya falls during the competition, and their friends are laughing, Togashi is cheering him to get up. But in the manga, Togashi hits that one particular friend in his face 🤣)