Hi @nabeeha63,
I believe what you're seeing is just the inherent design of Canvas and won't be easy to alter. When you say one thins is an assingment and one is a module, I think you might mean page instead of module. Pages will generally span the whole browser width, as there is only the page content to deal with. Assignments, on the other hand, have the "related items" column for teachers, which should have a link to SpeedGrader at minimum when the assignment is published. This may be a good news/bad news thing for you, because that column will generally only show up for you and not your students, meaning students will get a pretty similar view to what you see with pages.
I hope this explanation at least helps explain the differences you're seeing in the two items a bit!
-Chris