Sorry, Akiva,
Not an answer, but a specific question related to your questions, for when someone does answer:
I have the same question, but am particularly interested in the question of flare. Using my Nokton, I shot a concert last night where there was quite a bit of backlighting, and where it was not possible to avoid shooting directly into the spots on some occasion. I am wondering how the Sonnar might perform in such a situation.
My experience with Zeiss lenses is limited to the Contax T2 and T3 point and shoots. The T2 was especially good in similar situations.