Two Different Excerpt Length's

Try this function: https://www.transformationpowertools.com/wordpress/automatically-shorten-manual-excerpt

Or if you have many different excerpt sizes or want to show an exerpt outside the loop use functions like these: https://pastebin.com/aUZuQrZy
put them in your functions.php

And call the functions like this in your theme’s template file:

// inside the loop

my_excerpt(); // just a regular WordPress excerpt (55 words)
my_excerpt(30); // 30 words with formatting (<p>this is an excerpt ... [...]</p>)
get_my_excerpt(30); // 30 words without formatting (this is an excerpt ... [...])

// outside the loop
// pass a Post ID to the function (required outside the loop)

my_excerpt(30, 22); // 30 word excerpt of Post with ID 22
get_my_excerpt(30, 22); // 30 word excerpt of Post with ID 22

The functions both have two argument you can use

my_excerpt($excerpt_length, $Post_id);

These functions affect also the manual excerpt. That’s why they strip all html tags from the excerpt content. Otherwhise it might break your site

Your 2nd code sets the word number for the featured section but shows the full excerpt of the same post in the read more lower excerpt section.

Maybe it would be easier to only have the featured post in the featured section and not anywhere else on the page? Is there a code for this?

Or is there a code I can use that will set the word count of the manual excerpt only for the featured position?

Fantastic. Thanks Keesiemeijer!

Much thanks Keesiemeijer!!
Just what I needed.

If you use PHP > 5.3 you can make use of anonymous functions.

In your functions.php:

function custom_excerpt($new_length = 20, $new_more = '...') {
  add_filter('excerpt_length', function () use ($new_length) {
    return $new_length;
  }, 999);
  add_filter('excerpt_more', function () use ($new_more) {
    return $new_more;
  });
  $output = get_the_excerpt();
  $output = apply_filters('wptexturize', $output);
  $output = apply_filters('convert_chars', $output);
  $output = '<p>' . $output . '</p>';
  echo $output;
}

In your template:
<?php custom_excerpt(40, 'moo') ?>

Awesome, LordAzriel! But could I trouble you illustrate a PHP<5.3 version of the above?