Crikey, that was fun!  
 
 I had to be careful as this was on a heavily used live system but I have got this to work, by default and no messing about with config files. I was using a munin account (see my tutorial), so it complicated things due to having a different document root.
Results:
PHP Version 7.4.14
Server API    CGI/FastCGI
Virtual Directory Support    disabled
Configuration File (php.ini) Path    /opt/alt/php74/usr/php
Loaded Configuration File    /var/www/html/munin/php.ini
Scan this dir for additional .ini files    /opt/alt/php74/usr/php/php.d
Additional .ini files parsed    /opt/alt/php74/usr/php/php.d/imagick.ini, /opt/alt/php74/usr/php/php.d/ioncube.ini 
memory_limit   192M  <- changed specific to this account
user_ini.filename   .user.ini  <- this is being ignored, as it should, as not PHP-FPM (Edit: after-thought)
Notes:
GUI PHP Editor writes to /home/munin/public_html/php.ini (and replicates to .user.ini in the same directory)
  It should actually write to the munin.conf Document Root /var/www/html/munin - copied it to the correct place
PHP Selector writes the AddHandler to .htaccess, also rather than the Document Root - manually copied over.
Restart Apache 
Confirmed by adding:
disable_functions   exec, system, shell_exec
Restart Apache