It was the team bonus originally, but I was told that it was too broken.
The idea is that you can send other villagers to gather from the cows in order to get a bit of extra food that you don’t need to spend wood to get. Also, shepherds work faster than farmers by quite a lot, so it’s not an insignificant bonus if used correctly. It’s just not passive like many other eco bonuses, so players will have to actively use it.
Yes, they will. Boyars will be much weaker against archers and will probably have lower attack. They will be effective in melee engagements, but they won’t be all-around good like Knights.