Hi,
No, it will work with the registration done through Joomla or HikaShop's registration forms (AcyMailing doesn't have a registration form).
Regarding the username, I checked in the code of the plugin and it doesn't support it.
It would require some code modification to the acymailing-hikashop integration to support it.
In the file plugins/acymailing/hikashop/hikashop.php you can find this line which replaces the tags:
$code = str_replace(array('[name]', '[clean_name]', '[subid]', '[email]', '[key]', '[flat]', '[percent]', '[value]', '[prodid]'), array($user->name, $clean_name, $user->subid, $user->email, $key, $flat_amount, $percent_amount, $value, $product_id), $code);
Unfortunately, $user doesn't contain the information of the username and so to handle it would require loading the user with a MySQL query and then do the replacement. It's possible but it will require some development.