If you want to create a new user and have the value automatically filled such as the forum autosubscribe set to no and email set to disabled, what you need to do is to
edit the editadvanced.php which is located at your moodle/user/ folder.
Go to line 20, you will see if ($id == -1)
below that line, you can enter anything you want according to the database field.
Here is the example:
$user->auth = 'manual';
$user->confirmed = 1;
$user->autosubscribe = 0;