Unlike previous beta-testing because they happened under Shrapnels rules, this beta-test does not have a non-disclosure agreement. So I can actually say that I am beta-testing it and be able to answer specific questions. (I debated for while whether I WANTED to tell this community that I was in the beta but decided to chance the flood)
I would say that CoE2 is a great starting point, and then add on top of that the many lessons learned and increased skills gained from creating Dom3 (including things they wish they had done). That seems like it would be obvious but its the best explanation I can think of. CoE2 upgraded by Dom3 experience.