The planes get all cut up by traces and vias and pads and thru holes tho, so a VCC plane turns out not to be that useful unless you have a 4 layer board with dedicated power plane and dedicated ground plane, and leave the outer layers for signals. But then 4 layer boards are pricier. So ground on both outer layers and wider Vcc traces are all that is needed for Arduino and 8 MHz clk for SPI as the generally the fastest signal to worry about when the crystal is properly place next to the uC.