I was not able to find that information online. I saw that for desktops the power consumption does not go over 100W.
Laptops always have custom motherboards that do NOT adhere to ITX or ATX standards.
Those just wouldn't fit. In design they are (usually) conceptually close to ITX, but the form-factor is completely determined by the available space in the laptop casing.
Power-requirements are purely determined by the specs and use of the computer. That goes for any computer, not just laptops. There is even no such thing as a well-defined criteria what constitutes power-requirement for a motherboard. Do you count power consumed by RAM memory as "motherboard" or RAM? What about Nvme SSD? Mini-PCI Wifi adapter? USB devices without powered hub? These are directly powered by the motherboard, but are not part of it.