We don’t have a list. And its not always the parent container you need to style. For example as you’re using Separate Container for your layout, this bunch of element classes are used for Customize > Content Padding and Content background colors.
.separate-containers .inside-article, .separate-containers .comments-area, .separate-containers .page-header, .separate-containers .paging-navigation, .one-container .site-content, .inside-page-header, .wp-block-group__inner-container
I use the Browser Developer tools if i need to look up a specific class.
For the border radius – if you include overflow: hidden;
in your border radius CSS this will stop the menu item from poking out of the container.