2 ground planes vs ground and power plane for 4-layer pcb with many power rails
Something I've found very successful is to provide the currents from a bypass capacitor RIGHT AT THE POINT OF CONSUMPTION, and insert a SERIES RESISTOR of ONE OHM that comes from the regulator. 

Thus the VDD current surges have a Local Battery (bypass capacitor) to provide the fast surges, and some series impedance (lossy ferrite bead or lossy resistor.

I like the resistors in series, because the LOSSES are guaranteed to exist at all frequencies, unlike the poorly defined behaviors of a bead.

Additionally, for when you need really-clean-power, the resistor+Capacitor is a well-defined Low Pass Filter that helps with Switch Reg trash that crept thru that LDO which at high frequencies has ZERO ability to adjust its servo-regulator-loop to reduce the trash.

A 1 ohm resistor and 100uF cap have 100uS time constant and a F3dB of 1,600 Hertz.
Thus at 1,600,000 Hertz (typical switchReg trash/ringing frequency) you get up to 60 dB attenuation (the capacitor  ESR and ESL, and PCB trace resistance set the ultimate floor).

And that resistor DAMPENS. Well damped filtering is a fine fine thing.