Steam Deck.
From a pure physics pov - if you want high frame rate "flawless" (reading that as low latency) mouse/keyboard support - you want local hardware. The alternative is a local frankenbox, as per usual. But i think you'll be surprised at how performant the steam deck is.
@Biggles @Quinnypig maybe. I am concerned that my use case (my library of mostly Windows-based FPS games like Half-Life 2 and Doom 2016, running at a high frame rate and with flawless keyboard/mouse support) won't be well-supported on a Steam Deck. I guess I need to try yours out.