Linux also runs better on lower spec machines due to its better resource management. Reason a lot of people started using Linux back in the day so they didn’t need to spend 10-15k on a Sun Spac box and could use a 1-3k desktop
That's only true if you use DEs dedicated to low resource usage, which is not the case with KDE Plasma nor Big Picture.
Linux is actually worse at VRAM usage, and better at CPU multithreading. Either way, on a device like the Deck, there's no functional difference between Windows or Linux in resource utilization. The advantages of Linux are much more related to things like a custom compositor for gaming mode, not paying Microsoft licensing fees, and other experience adjustments.