Headings should always be used in order as if you are writing an outline. Copy should start with an H1 or H2 and subpoints go from there. They define how important the point is, and are not meant to be design elements. For example, an article can be setup like this:
Heading 1- main title
Heading 2 - First Point
Heading 2 - Second Point
Heading 3 - Second Point subpoint
Heading 2 - Third Point
Image with Content Block
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