HOW TO: customize/hide theme elements

How do I disable Header & Page Header by default across all pages & posts for all device types desktop/tablet/mobile?
Customizing > Layout > Header ?? no options
Customizing > Layout > Page Header ?? no options

How do I style the Inner Navigation Width seperate to Container?
Customizing > Layout > Container > Container width 800px
Customizing > Layout > Container > Primary Navigation > Inner Navigation Width > Contained ?? 1100px

I did it with the following CSS but wondered if there was better/existing options:

/* NAVIGATION WIDTH different from container */
.inside-navigation.grid-container.grid-parent {
max-width: 1100px;
}

/* HIDE CATEGORY header & duplicate images */
header#masthead, header.page-header, img.attachment-full.size-full.wp-post-image {
display: none;
}