I don't think there is any legit way to evaluate a therapist up front.

I've sat in front of 20+ of them, and each was a closed book and gave very little away. I've tried asking non-threatening questions, and some couldn't handle it. So, asking about their attachment status or mental health, that's probably not gonna go well with most. Plus, having worked on their own issues in therapy means nothing. It could easily have made them more neurotic. Add to that years of engaging in weird "clinical" relationships and they might have real difficulty relating in a healthy way.