Version 1.8.1 is available!
See release notes above.
Important change for the search path of the "Select aircraft" dialog within the profile:
Since this version you was asked to go to "Program settings > Platform specific settings > SimObjects" and enable each addon that contains an aircraft you want to fly with.
With this version all path are activ which can cause more loading time for SIMstarter NG cause all folder will be walked trough. As it doesn't make sense searching in AI Traffic folders like "Ultimate Traffic, MyTraffic, IVAO_MTL, e.g." it's better to disable this path in "Program settings > Platform specific settings > SimObjects".
Multiple versions of DirectX, like .NET Framework or SimConnect, can be installed side-by-side ("WinSxS"). Sometimes we can't use the latest DirectX because we have to make sure that things don't just work with Windows 10 but with 8 and 7 too.
The only technical things that have changed for CRJ SP1 is that the Prepar3D 4.3 SDK Tools have been used to build it (both DLLs and models). Other than that, Microsoft updates Visual Studio 2017 quite regularly, so there's another potential difference.
Regarding the DX setup error message, I don't know what it means, sorry. I googled the error message and found some advice from a Microsoft guy. Check here.