Hi, I have made the decision to buy an m200 and m600. The m200 is going to be included in my rotation of pens for school, the m600 stays at home. My question would be which nib do I choose for the m200. Will the fine be in any way scratchy, and if I choose a medium, will it be too wet? I have also herd that the nibs are removable. Will the m600 nib fit on the m200? Thank you for the responses.