Which font size setting takes priority?

I’m trying to understand font- size settings in the text editor module. I have a default setting under the customize panel of 20px for text. When I ope the text editor module, the default size is 16px. There is another tab in that module called “style”. Under typography - font there is an option for setting the font-size here too. Why are there two? Which one takes precedence (I can’t work it out with trial and error), and what’s the correct way to use them?