On efficiency side, there's big difference on OS department. Recently released handheld Lenovo Go S has both SteamOS (which is Arch btw) and Windows11 versions, allowing to directly compare efficiency of a AMD's Z1E chip under load with limited TDP. And the difference is huge, with SteamOS fps is significantly higher and and the same time battery lasts a lot more.

Windows does a lot of useless crap in the background that kills battery and slows down user-launched software