Hey Mark!
Thanks for getting back to us. While every person added to a MailChimp list is always a subscriber, it sounds like what you want to do could be accomplished through using either groups or a field indicating the type of subscriber in your list. This would really only be important if you’re using the same list for people of multiple types. If you’re using separate lists, then the lists themselves could be used for that separation.
If you want to take the field/group approach, then using our API to set up your own form would certainly be a great option, and an experienced developer should have a pretty straightforward experience with the help of our API Documentation.
An alternate approach would be using two forms via our Embedded Form code, rather than using the plugin at all, and modifying the code to set a particular field value, as indicated in this guide:
Can I set up my signup form so that I can see where my recipients signed up?: https://eepurl.com/SKbn
The important thing to note is you’d need to mark a user as the type of subscriber you want in a field or group at the time of signup using some sort of code customization unless you want to totally isolate the sets of subscribers by using separate lists, in which case there would be no crossover.
If you have any other questions, please let us know!
Thanks,
Gabe