For a given MCU, all other things being equal, does the memory capacity impact the power consumption ? A 512kB flash memory would consume more than a 128kB ?
No. Flash requires no power to maintain its data. It only uses power when actively reading or writing.
The amount of flash has mo direct bearing on the power consumption of the chip.
SRAM, however, does require power to maintain the contents, so the amount of SRAM on a chip vastly affects the power consumption of the chip.