You can allow TreeView's MultipleSelection and when the user selects a child node, you can make sure that the parent (or other custom logic) is also selected. That way the SelectionVisualBorder will stay for the items you want.
About ItemContainerStyle - its ok to have different Styles for each level, if you all levels looks different.
Please find attached an example.
If you have further questions please do not hesitate to ask us.
I hope this will help you.
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