does this plugin replace having to change the wp-config.php file

Don’t see a link in your post, but if it’s something like this:

if ( $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https' ) {
    $_SERVER['HTTPS'] = 'on';
}

the answer is yes, Really Simple SSL will insert that for you if needed.

Here is the link… a little different code

https://help.dreamhost.com/hc/en-us/articles/218428687-How-do-I-use-an-SSL-certificate-with-WordPress-

Add the following two lines above the line that? says “Stop Editing Here”:

define(‘FORCE_SSL’, true);
define(‘FORCE_SSL_ADMIN’,true);

These are not necessary. Redirects to https (which is what these lines do) are already handled by the plugin.