If the new Conservation coat fits the same as the Merino coat then you'd be between a III and IV. FWIW I wear IV in Merino it's more relaxed and loose but lets me layer. I'm also 36R. Maybe NMWA team can comment.
Yup I think the fuzzy conservation is my fave too. I love the charcoal lining. I like the twill one too but the navy lining looks slightly out of place because the contrast is too high.
I think the collar is slightly diff from my merino.