Windows' "Game Mode" is just suspending a few services. I mean a legit reboot of the OS into a stripped down kernal that doesn't a host of usual OS things, very similar to the Xbox consoles' stripped down OS. And there's a few reasons I suspect Microsoft's handheld would have a full windows suite. Firstly, their chief competitor isn't the low spec Switch, it's the high spec Steam Deck. Secondly, they'll struggle to produce a machine much cheaper than the Steam Deck because they're talking about allowing third party stores - so they can't price the hardware at a loss. So, if Microsoft launched an Xbox handheld that was the same cost or more as the Steam Deck, but one that had less features and/or worse performance, it would be DOA. So, I think they'll be forced to match price, which means matching performance, which means matching features.