In short, Pro has a single window interface and many more advanced features.
Pixelmator Team has made some amazing videos about some of the functions.
pixelmator Pro: http://www.pixelmator.com/pro/ Just pixelmator: http://www.pixelmator.com/mac/
Sorry, I don't think this feature exists, even with Vectormator.
I searched, gave up and bought Affinity Designer for 70$.
Cheers!