All the chimps they used in the Tarzan movies were females and, as with most films that use live animals, a number of lookalikes were available to film depending on the behavior they needed for each scene. Nobody with any sense would work with a male. They are about as large as a smallish human and incredibly strong and aggressive.
Once heard part of an old radio interview with Johnny Weismuller in which he was asked about working with Cheetah. I can’t remember it exactly after all these years, but I do recall that he said they always kept a sap handy in case Cheetah acted up.