The problem is, most dogs that are sized like you seem to want are not good for use as guard dogs against raccoons, foxes or coyotes, which are the predators you will mostly be dealing with.
Even a
LGD alone is not a match for more than one coyote at a time, but they will deter the coyotes from wanting to come around. Foxes are going to win against many medium sized dogs too.
We have three dogs, 1 Boxer mix, 1 Catahoula Cur, 1 Pit Bull mix, none of them are allowed in with the hogs and
chickens but they do patrol all around the fenced in area they live in.
We have a very large pack of coyotes that hunt the flat lands to the north of our farm, they do not come onto our
land because when they do their pre hunt calls, our dogs
answer.