"Up until today-Insiders who opted into Skip Ahead previously were receiving the same exact RS4 builds as Insiders in the Fast ring since Build 17017". The latest Windows Insider Preview builds for testers also include some emoji design updates to align with the standard emoji characters. Non-Skip Ahead users will get builds from the RS4_RELEASE branch.
The Redstone 4 update, build 17101, is being released to Windows Insiders in the Fast release ring and the Redstone 5 update, build 17604, to those in the Skip Ahead ring.
In addition to the new power scheme, the new Windows 10 testing builds enhance the UWP File System Access by giving more controls to you to decide which UWP apps can access your full file system. As a result, Microsoft is not enabling this on battery-powered systems, so this will only be available on high-end workstations.
Furthermore, when Windows 10 Pro for Workstations is initially set up, it will now offer business and productivity-focused apps, rather than consumer-targeted software and games, which certainly makes sense. "Just like other power policies in Windows, the contents of the Ultimate Performance policy can be customized", Microsoft says. While this power scheme is build upon the current High Performance scheme, it goes one step further to eliminate micro latencies associated with fine grain power management techniques.
Pre-release versions of apps including Paint 3D, Microsoft Photos, Windows Mixed Reality Viewer, and Windows Calculator will be available to try out.
A few days ago, Microsoft started opening up individual app preview programs.
It appears that Ultimate Performance mode may only be available when a laptop is plugged in (or not on laptops at all), as Sarkar notes that the "power policy is now not available on battery powered systems".