Hey Daron,

Meant to respond earlier but just haven’t had the chance. Prior to seeing your response I ended up working it out by doing it in the functions.php file globally for all widgets and seems to be working well for my purposes so far. For reference, the code i’m using is:

add_filter('dynamic_sidebar_params', 'before_widget_custom_classes');
function before_widget_custom_classes( $params ) {
	
	// get widget vars
	$widget_id = $params[0]['widget_id'];

	$hide_title = get_field('hide_title', 'widget_' . $widget_id);
	$border_color = get_field('border_color', 'widget_' . $widget_id);
  $custom_color = get_field('color', 'widget_' . $widget_id);
	$no_padding = get_field('remove_padding', 'widget_' . $widget_id);
	$col_width = get_field('column_width', 'widget_' . $widget_id);

	if ( $no_padding == 1 ) {
		$no_padding_class = 'no-padding';
	}

	if ( $hide_title == 1 ) {
		$hide_title_class = 'no-title';
	}
	
	if( $col_width || $border_color || $no_padding || $hide_title) {
		
		$params[0]['before_widget'] = preg_replace( '/class="widget/', "class=\"widget widget-{$col_width} border-{$border_color} {$no_padding_class} {$hide_title_class}", $params[0]['before_widget'], 1 );
		
	}

	if( $border_color == 'custom' && $custom_color ) {
		
		$params[0]['after_widget'] .= '<style type="text/css">';
		$params[0]['after_widget'] .= sprintf('#%s { border-color: %s; }', $widget_id, $custom_color);
		$params[0]['after_widget'] .= '</style>';
		
	}
	
	// return
	return $params;

}