Would this do the trick?
/** Full width Page Header with specific width for Content **/
// Overrides "Container Width" option in Customizer > Layout > Container
body .grid-container {
max-width: 100%;
}
// Manually set "Container Width" for the rest of the elements
.container.grid-container {
max-width: 1200px;
}
I was looking for the customization option for having the page-header to be “separated” from the main content too. 🙂