Can you get banned for playing COD Mobile on an emulator? No but I recommend using TenCent's official emulator, Gameloop. The word is that BlueStacks is a superior emulator, but by using it, you are violating the game's terms and are at risk of being banned.
By using the recommended settings, you will get the best possible gaming experience while playing Call of Duty: Mobile on BlueStacks 5. The recommended settings are as follows: BlueStacks settings: Set "CPU allocation" to "High (4 Cores)", "Memory allocation" to "Enhanced (4 GB)" and "Performance Mode" as "Balanced".