I love Files, and I see Excel files across platforms. But no way to edit them correct?

Microsoft now has excel as app, but I think you have the file reside with them. One drive. right?

An Apple store employee was saying you can edit them if you have Google Drive or Docs on you iphone, but I think he is implying you'd have to have the file reside there right?

I really like the icloud home base.. But we are helpless keeping the word/ excel files there? right? Always be read only?