M1's integrated memory is completely generic LPDDR5. It's the same stuff the rest of the industry uses, there's no power savings here (and it's not any more "integrated" than AMD & Intel have been doing for half a decade or more, either)

The primary interesting thing about the M1/M2's memory is the width of the memory bus, which is how it gets such huge bandwidth numbers. But if anything that's costing power, not saving it.