Is a NAND flash chip better for power saving purposes as a micro SD card?
There are a number of different NAND devices -
The ‘usual’ is a parallel interface like ONFI like you’ll find in usb sticks, ssd etc
There’s serial NAND that use a serial interface like SPI as the interface
Then we get into the ‘smarter’ flash devices that have a flash controller that implements things like wear levelling and bad block management like eMMC, usb sticks, sdcard and its variants.
I suspect this is what you want. eMMC will have the amount of storage you require. Effectively they are a sdcard in a bga package. I’ve not compared power consumption. You can find data on emmc from suppliers like Digikey. Kioxia is one manufacturer.