Visual Composer layout width is controlled via Row and Column options that allow you to define the width of the section. By default, the width of the row will depend on the content area of your theme or layout chosen in page settings.
Nevertheless, you can modify the width of your row via edit options to set it full width. Full-width rows and columns will also stretch all the content within the current row and column.
For example, if you have a text block in a row/column and the row is set to be full width, the text block will be stretched as well. The same principle applies to any other element of Visual Composer.