With "keys", is it the setting opcache.max_accelerated_files that you refer to?
opcache.file_cache=/.opcache
opcache.file_cache_only=0
opcache_hit_rate 99.98%
It constantly copies the memory to cache, which are disk operations. My bottleneck is the disk (it's SSD but it's loaded a lot) so I prefer leaving it off.
root@srv2:/home/cphpvb/public_html/test # touch test.php
root@srv2:/home/cphpvb/public_html/test # chown cphpvb:cphpvb test.php
root@srv2:/home/cphpvb/public_html/test # echo "<?php not_existing_function(); ?>" > test.php
root@srv2:/home/cphpvb/public_html/test # touch .htaccess
root@srv2:/home/cphpvb/public_html/test # echo "php_flag display_errors on" > .htaccess
rm .htaccess
root@srv2:/home/cphpvb/public_html/test # grep "php" /usr/local/directadmin/custombuild/options.conf
php1_release=7.1
php1_mode=php-fpm
php2_release=5.4
php2_mode=php-fpm
php_ini=yes
php_timezone=Europe/Sofia
php_ini_type=production
in cases like php-fpm, where .htaccess files are not available for php settings.