Google Fonts & Page Loading

Can I have a link to check the issues ?

First off, I also encounter the annoying “website appears unformatted briefly” myself when using bootswatch sub-themes, i will make sure to look into the issue, it should be fixed in the next release.

Secondly, the cerulean sub-theme overrides your choosing of font since -i am guessing- you have “style superiorty” ON in sub-theme options. Try turning it OFF and see if it works better for you (This time, some other things may be overriding cerulain styles, it’s a dilemma I know).

Or another way is to add

h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
 font-family: "Alegreya Sans",arial,sans-serif;
}

under Common > Quick Start > CSS box.

Of course, then you’d have to remember to change it accordingly manually, when you change your choice of font.

Let me know if I can help you with anything further.

BTW to solve the “website appears unformatted briefly” issue, you can open your functions.php and change

add_action('wp_head','eo_bswthemesup',9);
function eo_bswthemesup(){
	global $eo_options;
	$use_bsw_theme = of_get_option( 'use_bsw_themes' );
	$bsw_theme = of_get_option( 'bsw_theme' );
	if( $use_bsw_theme && $bsw_theme != "default" && $eo_options['bsw_theme_sup'] == "1" )	{
		wp_register_style( 'bsw_theme', get_template_directory_uri() . '/panel/of/themes/' . $bsw_theme . '.css', array(), '1.0', 'all' );
		wp_enqueue_style( 'bsw_theme' );
	}
}

add_action('wp_head','eo_override_css',1000);
function eo_override_css(){
	global $eo_options;
	$ov_cssf = get_template_directory().'/rsc/css/override.css';
	if ( $eo_options['override_css']  == "1" && file_exists($ov_cssf) ) {
		wp_register_style( 'bsul-override', get_template_directory_uri() . '/rsc/css/override.css', array(), '1.0', 'all' );
		wp_enqueue_style( 'bsul-override' );
	}
}

TO:

add_action('wp_enqueue_scripts','eo_bswthemesup',9);
function eo_bswthemesup(){
	global $eo_options;
	$use_bsw_theme = of_get_option( 'use_bsw_themes' );
	$bsw_theme = of_get_option( 'bsw_theme' );
	if( $use_bsw_theme && $bsw_theme != "default" && $eo_options['bsw_theme_sup'] == "1" )	{
		wp_register_style( 'bsw_theme', get_template_directory_uri() . '/panel/of/themes/' . $bsw_theme . '.css', array(), '1.0', 'all' );
		wp_enqueue_style( 'bsw_theme' );
	}
}

add_action('wp_enqueue_scripts','eo_override_css',10);
function eo_override_css(){
	global $eo_options;
	$ov_cssf = get_template_directory().'/rsc/css/override.css';
	if ( $eo_options['override_css']  == "1" && file_exists($ov_cssf) ) {
		wp_register_style( 'bsul-override', get_template_directory_uri() . '/rsc/css/override.css', array(), '1.0', 'all' );
		wp_enqueue_style( 'bsul-override' );
	}
}

Basically you need to change ‘wp_head’ hooks to ‘wp_enqueue_scripts’ hooks for eo_bswthemesup() function.