I prefer the Boxed Layout on Divi theme, but the big margins take away priority real estate on mobile and squishes all my content. I only want the Boxed Layout to work on Desktop / Tablet and would prefer Full Width on Mobile devices. The code below will accomplish that.
/*** Full Width On Mobile ***/
@media (max-width: 481px) {
.et_boxed_layout #page-container {
max-width: 100%!important;
width: 100%!important;
}
#main-header, #top-header {
max-width: 100%!important;
width: 100%!important;
}
}