Just come back from a week on OV2. We were in a BB grade cabin - big floor to ceiling patio door leading to balcony with railings. BC grade below us had balconies enclosed in the bulkhead of the ship. Basically in BC cabins you have to stand up to get the view, while BB cabins you get the whole view.
Not very clear the BC cabin has floor to ceiling windows and patio door leading to a balcony with chairs and a table and a solid fronted balcony. The patio door is not mentioned in the BB cabin but it does have a balcony so the access and the solid fronted balcony are the only difference, so not to helpful I am afraid.
I have just booked on OV2 and chose a BB, I have not been on OV2 before, but I have been on ships with the solid fronted balcony the same as the OV2 BC and find they feel quite a bit more enclosed than the type of balcony you get in a BB grade.
Hope this info helps.