Hello,

In order to control these fields is enough to use the Advanced typography functionality. Please, navigate to Theme Settings -> Typography -> Advanced typography -> create a rule with the “Product grid title”, “Single product title”, “Blog post title” items and set any font size for it.

https://monosnap.com/file/P3DAgKjmXaLXm78ZFFyt9ScTclPZgD

Please let us know if there is anything further we can assist you with!

Kind Regards