Explosive throws should be totalled, due to the CNS effect, but they are not the same as Plyos and the numbers will not be the same and will not be interchangeable. Some Plyos involve smaller numbers of motor units, but are even more intense and involve the same motor units as sprinting, while some explosive throws can spread the load over different MUs, so the numbers will tend to be be higher, depending on the emphasis on the weight program.
The overhead backward throw might involve above 80% of the motor units and is high intensity. Using this as a rough guideline, you can decide on numbers based on the volume of work being done in the other high intensity elements, based on their motor unit involvement and intensity.
So many variables…all with different motor unit involvement, relative intensities and CNS ‘cost’. How to apportion volumes of each over different sessions at different stages of the year - the art of coaching?