Hello Patrick,
Thank you for your question.
LayoutMode is a nullable property (of type DocumentLayoutMode?) and for some reason it cannot be set through a style using the "normal" syntax, even though it usually shows in the designer.
However, you can set it like this:
We didn't observe any issues with the property IsSpellCheckingEnabled. I hope this helps!
All the best,
Vasil
the Telerik team