Whats the difference? Heres how Microsoft explains it:
For the most part, the Direct3D code in a Universal Windows App is largely the same as a Win32 app. There are some changes to the core Windowing system, which mostly effect how full screen windows work. There are no performance differences between a DirectX 12 UWP app and a DirectX 12 Win32 app.
Even if you presume thats true, theres fewer options for players, which is why Microsoft had to issue an operating system update.
That update brings, as I said, support for G-SYNC and Freesync, in addition to unlocked frame rates. The former helps keeps game smooth: