What are the consequences of having a work and personal iPhone with the same Apple ID?
You can use the same Apple ID and as you wrote, apps, music, books and so on are shared between devices.

Regarding Photos, you can turn on/off syncronization (Settings -> [your name] -> iCloud -> Photos, then turn on/off iCloud Photo Sharing)

Regarding iMessage you can turn on and/or off this feature from your phone (Settings -> Messages)