Heavy writers used to a Lamy 2000 will usually find the regular Mid-Size Bohème too small and too light; the two pens differ fundamentally in size, weight and ink capacity. The Bohème was offered as a Mid-Size with a stone in the clip and a retractable nib and as the no-longer-produced Big-Size Bohème Platinum the size of a Meisterstück LeGrand without a stone in the clip; only the Mid-Size has a stone, and only the Big-Size reaches the size of an everyday LeGrand, although there too the nib is retractable. Nib widths such as OB or OBB are not standard and are little suited to everyday use, but rather signature nibs. Collectors strongly advise buying from an authorised specialist dealer rather than online, because there nib widths can be exchanged subsequently and originality is guaranteed.
Related pages on fountainpen.de:
• Montblanc Bohème — model overview: https://www.fountainpen.de/boheme-en.htm