Slitherine

I watched the Das stream. He took over the 4 region province including Crete by using those regional decisions. I had a couple questions about that:

1. Does the region I win over drop into turmoil like it would if I captured it w an army?
2. Was this partly how Persia grew so large so fast?

1. No, this is a friendly control
2. No, Persia can get the entirety of Media once the capital fall and after some turns, unless Media is Glorious.