The question about the doggy smell is a good one - basenjis do not smell like dogs. If you stick your face right into their fur the comparison is like sticking your face into a nice clean healthy cat - warm and not really a discernable smell. Except their feet. Their feet smell like Fritos sort of.
All dogs that are treated well will be good protectors.You want big dogs means like Labs, German Shepherds, Doberman Pinschers, etc. or any mixed breed dogs will do as well.