AppThemes does not officially support third party plugins, so we cannot guarantee that all plugins will definitely be compatible with our themes. Whilst there are plugins such as
SEO by Yoast that are commonly used by members of our community, others such as BuddyPress may not work directly "out of the box" based on some feedback from those who have tried it, and could require additional customization in order to work. Some recommended plugins can be found
here.
There is no encryption in Vantage which would prevent you from making modifications to the theme for a slider, so you are free to make such changes if you wish. How "easy" this is, is ultimately related to your level of coding knowledge.
The question of membership is related to WordPress more so than the theme itself, and the number or users it can handle virtually unlimited. Consideration should be given to the actual hosting of your website for this kind of thing, and
this WordPress documentation contains some useful information for high traffic websites which may explain things in more detail. Thanks.
