Tessitura Transition Question - moving from MailChimp to Wordfly/Prospect 2

Hello! We are in the process of moving to Tessitura, with a go-live scheduled for later this spring. 

We currently use MailChimp, and will be transitioning to either Wordfly or Prospect 2 (still TBD!). At the moment, we are essentially managing two databases - buyer history and list pulls happen in our CRM, but our email data all lives in MailChimp.

I'd love some advice from anyone who has made this transition, as far as specific setup questions, such as: 

-Did you integrate your existing email data into Tessitura somehow? How did you go about this? Any pitfalls to avoid? I'm especially worried about duplicate accounts.   

-In MailChimp, we have many "interest groups" that someone can elect when they manage their own profile. Those interests may or may not match their buying behavior to date. Should I reconstruct those lists in the new ESP? 

-We have many contacts on our MailChimp email list who do not have a profile in our CRM. They may have signed up on our website, Facebook, etc. Where should I keep those folks? Should I move all, or only focus on people who have recently engaged with our emails? 

-How to manage communication preferences. For example, there may be people who indicated "do not email" in our CRM when purchasing a ticket somewhere along the way, but have actually opted in to our emails in MailChimp. Which one "wins?" 

-In your current setup, if someone signs up for your emails, do you create a Prospect account in Tessitura of some kind? Or does that contact only live in your ESP?

Thanks very much for any advice, on the above questions and any I may not be considering as well!