CSS files, that load in <head> section of page in the current template are the following:
<!-- Theme Styles CSS -->
<link rel="stylesheet" type="text/css" href="css/plugins.css">
<link rel="stylesheet" type="text/css" href="css/theme-styles.css">
<link rel="stylesheet" type="text/css" href="css/blocks.css">
<link rel="stylesheet" type="text/css" href="css/widgets.css">
<link rel="stylesheet" type="text/css" href="css/font-awesome.css">
<link href="https://fonts.googleapis.com/css?family=Playfair+Display:400,400i,700i,900," rel="stylesheet">
• Plugins.css – styles of all theme`s plugins
• theme-styles.css - main site's stylesheet;
• blocks.css – styles for blocks and template components;
• widgets.css — styles for widgets;
• font-awesome.css — styles for the icon font “Font Awesome»;
https://fonts.googleapis.com/css?family=Playfair+Display:400,400i,700i,900 — connected external font file