For those interested, the following was received from Support:
K15003: Data plane and control plane tasks use separate logical cores when the BIG-IP system CPU uses Hyper-Threading Technology
The even-numbered hyper-threads (0, 2, 4, etc.) are dedicated to TMM as a high-priority process to service data plane tasks.
The odd-numbered hyper-threads (1, 3, 5, etc.) process control plane tasks at a normal priority level
Per K15003, odd-numbered cores are dedicated to control plane tasks while even-numbered cores are dedicated for data plane (TMM).
Therefore, you are likely not noticing any sort of traffic impact (as that's handled by TMM and is part of the data plane) but seeing high CPU usage due to other control plane processes on core 1 and 3.
Also
To copy a certain policy in the same unit with different name means to add huge configuration (depend on how complicate), it would impact the system in a certain degree.
We would recommend you to run "export" option rather than "copy". Export the policy base on existing policy configuration this will lighten the system performance and resource usage.
The above recommendations significantly reduced the CPU usage and have sped up our whole process.