Regarding the number of catapult on 003 being 3 instead of 4 as USN, here is a research paper from 2016 by China Ship Development and Design Center. Title "基于闭排队网络的弹射器数量配置方法"/"Method of the catapult quantity deployed by using closed queuing network"
Here is the conclusion,
Based on data from Nimitz 1917 high tempo exercise, the research concludes that 2 catapults are enough.
From table 2 and the diagrams, it can be seen that only when T_launch=6min, 2 catapults will be close to 100% used which is too much. In all other cases, there is enough margins. This means 2 is the minimum and runs some risk of overloading the catapult. 3 is as good as 4. 4's redundancy advantage then 3 is visible but insignificant.
Here is the conclusion,
Based on data from Nimitz 1917 high tempo exercise, the research concludes that 2 catapults are enough.
From table 2 and the diagrams, it can be seen that only when T_launch=6min, 2 catapults will be close to 100% used which is too much. In all other cases, there is enough margins. This means 2 is the minimum and runs some risk of overloading the catapult. 3 is as good as 4. 4's redundancy advantage then 3 is visible but insignificant.