Chimpegration works exclusively with the List functionality in the webview of Raiser's Edge NXT. While this can offer additional functionality not available in the database view (such as the option to select users within a specific radius on the map), it may also limit the fields are available for Export from Raiser's Edge NXT to Mailchimp as well as the options for grouping.
The functionality and limitations of this option are constantly in flux as Blackbaud changes this tool.