Hi Reid. Good questions.
I'm starting to look into this myself with our set up. All I an say is if you look here (https://docs.moodle.org/dev/HTML_Guidelines#Header) and here (https://docs.moodle.org/dev/Standardize_classnames_and_layout_to_facilitate_theming#Header_usage_should_be_hierarchical_within_page_views) it explains when and why H1 and H2 tags are used and why everything else is H3. I hope that answers some of your above questions.