MUI2 Documentation

Who knows where to find documentation on MUI2?
I still have not found any guide on how to use MUI2. 🙁

From the (few) resources I found so far, I only believe to have learned that...

a) MUI2 is a fully new UI instead of just a newer release of MUI,
b) MUI2 is still in beta state,
c) MUI2 is used differently from MUI.

Are the above assumptions true?

OMG!
What's this?!?

OMG! What's this?!?

Sort of magic, I think. 😉

Why the heck isn't that linked to when searching the NSIS main page for "MUI2", or from the documentation itself?

Anyway, thank you for opening my eyes!