TL;DR: Antec is going to be selling a Steam Deck competitive device, based on the Ayaneo Slide. The device has a slide up screen that reveals a keyboard, which is good because using desktop windows is much easier with a keyboard. However the device's lowest estimated power draw at low/no load is 15w, meaning it will use comparable power to the deck running at max power. This means the battery life will probably be pretty rough when compared to the Deck. It will also likely have a much higher price point.
I understand what you're saying, but that doesn't have to be true. Many of the games are made to be run on windows, windows is still a effecient os, it's just a lot of bloat, which can be disabled. Also a lot of optimizations in nt has been done for gaming, features which are missing in the linux kernel, but there are RFCs to add nt like synchronization primitives, in the linux kernel.