This is H1 that is only used by your design for titles, I don’t use it to write

This is H2 that I sometimes put above the image for the post if it needs a seo boost

This is H3 that I use on captions to differentiate them from text text (and when I have a caption box attached that is grey background)

This is normal text text like paragraph

This is H6 that I use in caption boxes that don’t help SEO, but look just like H3

H4 is the same turquoise helvetica lt as used for titles of categories, I use it sometimes too like on
https://www.solarpaces.org/worldwide-csp/csp-potential-solar-thermal-energy-by-member-nation/china/

H5 is more for the researchers paragraph headings a bit different than simply using

bold in paragaph like this actual bold