What is the difference between system clock and peripheral clock in case of arm Cortex M4 architecture?
You're mixing up MCU core architecture (e.g. "Cortex-M4"), which is the same for all ARM Cortex-M4 ICs, no matter whether they were designed by NXP, ST, SiLabs,…, and peripheral design, which was done by whoever took ARM's processor core design and integrated it with peripherals to make it a MCU.

So, no general answer can be given. Usually, peripheral clocks and MCU clocks are coupled through some clock dividers or PLLs, but that's not always the case.