RTX3090 is a desktop part optimized for maximum performance with a high-end desktop power supply. It isn't meaningful to compare its performance per watt with a laptop part.
Saying it offers a certain wattage worth of the desktop part means even less because it measures essentially nothing.
You would probably want to compare it to a mobile 3050 or 4050 although this still risks being a description of the different nodes more so than the actual parts.
It's no comparison at all, the person who bought a 3090 in the 30xx days wanted max gaming performance, someone with an Apple laptop wants longer battery usage.
It's like comparing an F150 with an Ferrari, a decision that no buyer needs to make.
Saying it offers a certain wattage worth of the desktop part means even less because it measures essentially nothing.
You would probably want to compare it to a mobile 3050 or 4050 although this still risks being a description of the different nodes more so than the actual parts.