Well, as i said, use the wc registration form is not an option because there is another plugin handling the user registration, i just would like to trigger WC’s new account email even when the account is being made by the default wordpress system or by another plugin.
The good news is that i got a solution, i will leave here.
if someone one day needs a solution like that, this simple code worked for me:
function send_welcome_email_to_new_user($user_id) {
$wc = new WC_Emails();
$wc->customer_new_account($user_id);
}
add_action('user_register', 'send_welcome_email_to_new_user');
if there is any suggestion ou someone wants to improve this little code, would be nice!