i dont recommend reading the manga. read the novel, light novel or web novel. wb is fully translated.
but anyways, first thing is how the manga pushes about 25 books into a couple chaptes, and by doing this, skips alot of IMPORTANT details. the other part is the atmosphere, the wb successfully made a serious, dramatic comedy. and introduced the plot and foreshadowing perfectly, while the manga is kinda like, "how d'ya like this arc... what about this?". the manga is more comic and just less serious. also, i dont like the art. the manga is much mroe full of cliches and stereotypes of the like, but the mushoku tensei novel is very famous for standing out. the mc always tries to hide the bad stuff, that is what makes his character, but here its like they REALLY want you to see that he is able to get sad. the manga is really cencored compared to the novel, in a way that kind of ruins the characters, cause the novel uses sexual themes as en element in comedy and drama, but the manga is more censored.

in the novel, you're really experiencing the mc's thought and actions, and you grow more attached to him, the same with the otehr characters, but in the manga, its super generic. an example: you skip the part where he learned the rare "chantless incantacion" in the manga, and they just show you how talanted he is... but in the novel, he manages to do it by an accident. the manga is like a super shounen jump version the dark dramatic comedy known as mushoku tensei. the manga kind of just makes mushoku tensei seem like pure fiction that is just funny and has a good plot, but it really ruins the potentiall mushoku tensei originally has. read the novel instead.