power signal layer mixed pcb
top
L2GND or L2VCC
L3VCC or L3GND
Bottom
high speed signal can routing in top(when L2GND) or bottom(when L3GND).just reference to GND plan,
For EMI, you need keep 20h rule. the power plan need smaller 20h than the GND.
For Mixed singal, you need use the moat for different signal's isolation
some time we need use the EMI cap to across the moat, and analog signals need come out from one gap area.
For impedance control, you need device to singal ended and differencial pair, and the pair signal should be refer to GND plan.
10 MHz is not so high, so you can make sure the power plan is a GND around the power, and all GND is better.clock signal need to routing in a reference to GND plan too.
that's my experience for these year's PCB layout,any other good idea will be given by next friend,hope wish you a whole success on your project process.