I checked game.PlaceId both online and in edit mode and they are the same. I was confused by this wiki page where it says "To access it, open place from website (for example, from Start Page->My Projects)" because the example "Start Page->My Projects" is the opposite of "open place from website." I tried start server and start player and the data wasn't the same there either. What is the actual correct method of accessing DataStore keys from studio?
The simple answer; The online mode uses ROBLOX Cloud Service
Edit mode does not. It only access the cloud service while you are Saving and Opening. Even during Auto-Save, it only uses local services.