If the distance is short and uncomplicated between the battery positive terminal and the buss bar, then no protection is demanded. En example would be mounting the batteries then passing cables through a wooden partition. Both batteries would then be wired to the buss bar then things coming in and out of the buss bar would see a circuit breaker at each cable or wire.
(1) battery 2 cables. One positive and one negative. The buss bar does all of the manifolding. Battery cable count should be kept to the bare minimum.