alceste
Hi,
For the registration redirection issue, you can change the same settings in the plugin as I mentioned in that thread.
Regarding to the intro text for the registration form, you can customize the layout file of this registration form in template a little bit.
Open the file: /templates/gk_storebox/html/com_users/registration/default.php
Above the form, you can add your text there:
<div class="registration-desc">
<h4> This is registration form, blah blah</h4>
</div>
Like this: