Farming carrots and onions and turnips is definitely more efficient. I think it is because one cannot find carrots and onions and turnips in Valheim; one can only find carrot seeds, onion seeds, and turnip seeds.

Farming is not a matter of efficiency. It is a matter of necessity if one wants carrots or turnips or onions.

As for deer as livestock, yes, it is used a such by Lapps by Lapps who have no alternative and bred in the United States of America because the U.S. Depatment of Agriculture will not allow the commercial sale of wild meat. Vikings, however, had alternatives and did not have the USDA so they did not tame deer. So they did not tame deer.