Should I use the same Apple ID passcode for all my devices?

Sorry, your question is not very clear.

Apple IDs use passwords not passcodes.

Passcodes are used to unlock a device to be used, but they have nothing to do with an Apple ID.

If you are using the same Apple ID on all devices in Settings, then by definition they have to be using the same Apple ID password to log into the same Apple ID. You can't have different passwords for the same Apple ID.

Are you asking if you should have the same passcode to unlock a device or are you asking if you should have the same Apple ID for all devices you own? Or something else entirely?

In general, devices you own and use should be using the same Apple ID and by extension the same password for the Apple ID.

Devices used by other family members should use their own Apple ID and password.

If you are referring to something else, then please clarify.

I you are the sole user of the devices and want all the data shared between them, then yes. If they are for different family members or users, then no.

Make sure that each family member has a unique Apple Account - Apple Support

Even when you are the sole user of the devices, there is a use case for having a different Apple Account. For example, if you have work devices and personal devices, it may not make sense to share the data between them. You may want to keep different Contacts or Messages for a work device then what you would want on a personal device.

Ah yes! I read it as Password.