Microsoft has affirmed that Windows Store UWP games may leverage the most out of Windows 10's new Game Mode feature, which re-allocates system resources to boost in-game frame rates. However, this rate won't be anything dramatic, and games will see as little as a 2% FPS boost.
Xbox program manager Kevin Gammill recently opened up to Ars Technica about the new Game Mode feature that will help optimized Windows 10 PCs for gaming. Gammill says that while Game Mode supports both Win32 and UWP games, the latter may see "slightly better" FPS boosts.
Game Mode can improve in-game frame rates for CPU and GPU-bound games from anywhere from 2% to 5%, so this may not be a dramatic boost depending on the game. Also it's interesting to note that the possible performance boost disparity is due to Win32 games being able to launch extra processes, whereas UWP games are more lightweight and this respect and can't install background services and whatnot.
But how exactly does Game Mode work? Microsoft already confirmed that the feature "will prioritize CPU and GPU resources to your game running in your foreground," and that Game Mode will help improve two forms of FPS--overall high peaks and consistency.
According to Ars, Gammill hinted that Game Mode works by "suspending or deferring unnecessary background tasks and using process priorities and processor affinity to limit any performance impact of multitasking."
Game Mode will be available in the immediate future for Windows Insider testing, and will roll out to the public in the Windows 10 Creator's Update this Spring.