Anurag Gupta

Thanks for getting back to me.

1. When a user completes the popup form, are they then “subscribed” to your site, or is this information only submitted to Mailchimp and they are not actually logged-in users on your site?
Yes, they should be subscribed to a list and tagged with category and sub-category-based segmentation in Mailchimp, this will be used for further email marketing and CRM. An integration with FluentCRM ( a WordPress alternate to Mailchimp is most desirable ).

2. I believe you could use the WP Fusion integration. I am trying, thanks.

The downside is they need to be logged in
Unless they log out, on the next visit they should see the site based on the last visit action. Also, we can set cookies for X days.

3. Say the user indicated that they were interested in “fashion” when the form is submitted the page URL could become something like http://www.example.com/?interest=fashion.

I suggest you Check top10.com, the URL remains the same, but the content in few blocks updates based on user choice ( he can select multiple categories and subcategories associated with each category ).

4. Another suggested plugin If-so, just explore. It will help you with more features in the upcoming update of ADD-ON in PRO Version.

Thanks for all the suggestion, will explore and get back to you.