HELP with SEO for 4 custom fonts (how to structure)

Hi!

My client has 4 custom fonts that will need to be coded into the website. 

My question is, what would be the best way to structure this between headings and paragraphs? As I know this will also play a role in SEO. 

E.g. Would you make the "Subtitle/Tagline" font (which is a script/handwritten font) H4? Or H3? Or neither? 

OR

Would you make The H1 the serif, H2 the handwritten in the same size, and then do the same for H3 and H4 in a smaller size?

These are the fonts: 
x2 Serif (1 regular / 1 italic)
x1 Script / handwritten
x1 Sans Serif 

It's a bit of an awkward question, so hopefully someone understands what I'm getting at. Haha. 

Any help is appreciated! Thanks 🙂