How to Change Font-Size Twenty Seventen The Right Way ?

Hy. I was installed wordpress 4.7 before and starting using themes twenty seventeen.

This is great theme.

I have replaced default font (font-family: “Libre Franklin”) with my google font choice, but the text is too small.

I am newbie to CSS. I was read article before about ‘rem’

I read the parent style.css and there is “rem” for font-size. Am i true if using this css to change the font-size.

html{font-size:18px;}

I am using that style to change the default base rem size (16px to 18px).

I am afraid about browser compatibility.

Am i right using that or i must change one by one font-size for every elements (I hope i am not using this method) ?

Thanks.