Does Font Manager load all fonts on all pages?

Hi there! I really dig the new font manager and have a question about how it works.

Does this load all the fonts chosen on all pages? Or do fonts only get used if they are called for by an element on that page?

I have a website which will use a different header font for different sections and just trying to figure out the best way to approach this, whether it's safe to use the Font Manager or if I should stick to something else to make sure they only load when needed.

Thank you!