Sorry for the late reply, I was too busy to make a thorough test in weekdays.
I also have this confusion for ChromelessWindow. In some cases ClearType works, others don't. I'll show you what I found.
This time I uploaded 3 solutions together with their screenshots:
1. DefaultFontRendering: This is created solely with WPF built-in controls. Of course it works correctly. If I set "TextOptions.TextRenderingMode" as "ClearType", I can see ClearType, and If I set "TextOptions.TextRenderingMode" as "GrayScale", I can see GrayScale.
2. SfFontRendering: The only difference between DefaultFontRendering and SfFontRendering is switching from Window to ChromelessWindow. This time, I can only see GrayScale no matter what value I set to "TextOptions.TextRenderingMode".
3. SfWithMetro: The only difference between SfFontRendering and SfWithMetro is adding syncfusion:LayoutControl.SetMetroMode="True" to SfWithMetro (and a reference to Syncfusion.SampleLayout.dll). This is the same method used in your demos. This time, ClearType and GrayScale options works again, although the window is a ChromelessWindow.
Note that when used ChromelessWindow, the rendering details of Chinese texts are different from system default.
And back to my first post, when the window is a RibbonWindow, even setting syncfusion:LayoutControl.SetMetroMode="True" cannot make ClearType work.
The issue occurs no matter what characters I add to the app. For the SfFontRendering project, even if I remove all the controls, I can still see the "MainWindow" title rendered using GrayScale.
Also, the issue occurs in all the Win7/Win10 computers I can find (Win7 also have this issue. See SfFontRendering/win7.png), The system language of them are all Chinese (Simplified).