But it's up to you, of course. This is only style/fashion or whatever, and it's all personal and subjective. I happen to think doing these things makes the coat look better, just as I think buttoning only the middle button on a three-button blazer looks better. And I base a lot of this on the way I have seen the pea coat worn.
I don't know. Check out some images and decide for yourself: Googled images of pea coat wearin'