First time I see vinegar mentioned. I usually put a tablespoon or so sprinkled over the cabbage rolls before cooking and if available the skin and fat from a baked ham. Delicious. Keeps the rolls lovely and moist and the vinegar adds a certain taste to them which is enjoyable. There are so many versions of cabbage rolls but it is a personal preference which one uses.
I prefer very little meat. Perhaps salt pork in little pieces sautéed with the onions and then mixed into the rice. One charrizo sausage squeezed out of its casing is also delicious sautéed and added to them. Happy cabbage roll making to all.