Redux is to React what the 'update' function is to Elm architecture (first code example in the following link)

https://guide.elm-lang.org/

Answering your question, the difference is Elm has a more expressive type system than javascript, and will catch a lot of errors for you, with excellent error reporting from the compiler.

The layout of the code becomes less important, because the compiler will catch most errors (actually recommended in elm guides not to split in too many files until overwhelmingly necessary)