If Studio Access to DataStores is enabled that means you can read/write to the live DataStores for that place. That means you can overwrite existing data and potentially lose data. But it’s also good for editing data within studio with plugins such as sleitnick’s DataStore Editor.
Regarding reliable Datastores, I would recommend ProfileService. It is an op module that handles all DataStore stuff reliably and automatically and you never have to worry about it. It is very popular and used by many pro developers.