Conditional Page Title or Page Header

I am working to build a GeneratePress Header Element with a conditional page title.

Using Advanced Custom Fields, I have created a custom field named "page_headline"

By default, I would like to display the regular WordPress page title. However, if a value is entered for "page_headline" I would like to display it instead.

I've attempted to accomplish this two ways. The first was by defining a shortcode that I entered into the GeneratePress Header Element. Although I could get the conditional logic to work, the shortcode displayed outside the page-hero area. More specifically, the shortcode displayed between the "header-wrap" div and the "page-hero" div. The code I used for that shortcode is as follows:

function dg_conditional_page_header() {
    if ( get_field('page_headline') ) {
        // Display ACF Page Title Override
        echo '<h1>' . get_field('page_headline') . '</h1>';
    } 
    else {
        // Display Page Title if no value set for "page_headline"
        echo '<h1>' . get_the_title( ) . '</h1>';
    }
  
    if ( get_field('page_teaser') ) {
        echo '<p>' . get_field('page_teaser') . '</p>';
    }
  }
  add_shortcode( 'dg_page_header', 'dg_conditional_page_header' );

With the above code displaying outside the page-hero div, I turned to attempting with a Hook placed at wp_head. The code I used for the hook (which didn't work) was as follows:

if ( get_field('page_headline') ) {
        // Set PHP $headline variable to ACF "page_headline" field value
        $headline = get_field('page_headline');
				apply_filters( 'the_title', $headline );
    } 

Nonetheless, any help or insights into what I'm overlooking are greatly appreciated.

Thanks in advance.