Denis,
The LDO configurations really depend on your system power specification. You can use the 3.3V as an input to the 1.2V LDOs. You just need to make sure the main LDO (5V to 3.3V) has enough output current capability and thermal requirement for the additional current draws.
Ferrite bead is simply an inductor with lower Q and broader impedance across AC. Like an inductor, it passes DC voltages. The AC impedance "filters" out the noise and passes only the DC voltage.
The FB30 is similar to a capacitor with the third terminal connected to ground for better EMI suppression. The goal of the ferrite bead or FB30 is to provide clean power supplies for the DAC.
http://search.murata.co.jp/Ceramy/image/img/PDF/ENG/L0111S0111NFM31P.pdf
You can contact your Murata rep for more details and further recommendation for your power filter design.
-KH