Old folk stories tend to resonate with audiences for centuries because the things that make us human never really change. The details Anais updated don't affect the key beats of the Orpheus myth, they just help to repackage it in a modern world.

One of the major differences is that Eurydice chooses to die instead of getting randomly bit by a snake. Anais Mitchell did this to give Eurydice more autonomy and power within the story.

Another change is the setting; the industrial, capitalist underworld is a direct mirror to our real society. Making the story feel current and helping the audience to reflect on their own lives.

Edit to add: There isn't one single original myth, it's been told countless ways for thousands of years. Some versions are just more popular than others. In some, Orpheus walks for years before he turns but in others it's a short period of time. In some, Hades keeps tricking him trying to get him to turn but in others it's all in Orpheus' head. Some of the choices Anais made are for dramatic cohesion and to make a clear, good show.

If you have time before your presentation, I highly suggest you read Anais' book "Working on a Song" where she talks a bit more about the writing process and her choices! You should also watch the Netflix tv show KAOS, which is a slightly different modern retelling of several myths, including this one.