Let me answer your questions...
1) We haven't added virtual space to the WPF version yet, but it is on the TODO list.
2) The LexicalParsingEnabled feature was more of a feature for last-resort handling of bad performance scenarios in the WinForms version. Performance on large files is much better in the WPF version, so we never added it in. Do you have a need for it?
3) While we don't have a property in the WPF version, you could unregister the IParser service from your syntax language to turn off parsing.
4) Do you mean the Document.AutoTrimTrailingWhitespaceOnPaste and AutoTrimTrailingWhitespaceOnTextReplacement properties? We don't have that feature in there right now but will add it to the TODO list.