I'm trying to customize font sizes a bit, as I generally find them a bit too small for my liking. 

To change the font size for the text inside the forum posts, I went into my theme > Font Scale, and changed "Medium Text". However that also changed the size of the last post titles listed next to each forum on the home page. Is there a way to avoid that?

I also would like to change the default font size for a <p> element in Pages, and I'm not sure which one to change?

Thanks!

Each text element is under one of those categories (medium for example), and so would affect more than one area. If you wish to change the font size of one item specifically, you would need to customise this in CSS in your theme. 

1 minute ago, Marc Stridgen said:

Each text element is under one of those categories (medium for example), and so would affect more than one area. If you wish to change the font size of one item specifically, you would need to customise this in CSS in your theme. 

Ok thanks Marc. 

Is there a way to tell to which category a text element belongs to? For example the <p> element in Pages? 

You would need to take a look at the CSS files on your theme. For example is you look at core.css you will see right at the top you have the following, which shows you that ID uses the font size associately with 2x_large

#elErrorMessage {
    margin-top: 0;
    font-size: {fontsize="2x_large"};
    font-weight: 500;
    line-height: 1.4;
    max-width: 800px;
}

Great! That makes sense. Thank you. 

No problem at all 🙂