There is a blog post floating around explaining exactly how much workbooks in particular were shown to be around 80-90% as effective as in person IIRC but I can’t find it right now. Also IIRC Anxiety is one of the more responsive to treatment disorders.
Popular take: http://www.scientificamerican.com/article/are-all-psychotherapies-created-equal/
There is a blog post floating around explaining exactly how much workbooks in particular were shown to be around 80-90% as effective as in person IIRC but I can’t find it right now. Also IIRC Anxiety is one of the more responsive to treatment disorders.