Exceeding the subscription plan storage will have minimal impact on your activity. You will still be able to access all cases, communication, video call feature (if you have a paid plan or an older free upgraded plan), request payments, collaborate with unlimited doctors, create new cases, upload new documents and investigations, and many more.
The account limitation regarding storage only applies to older imaging investigations that exceed the plan limit. So, for example, if I have reached exactly 20GB of investigations in my account, and I upload one more investigation, only the older investigations that cannot be included in the plan limit will not be accessible to you— not being accessible means that you will not be able to open it with the DICOM viewer. The investigations that exceed the plan storage limit will not be deleted, they still belong to you, and you will be able to access them once you upgrade your storage plan.
The idea of this account limitation is to allow you to work uninterrupted even when exceeding the storage limit, and it only applies to the oldest imaging investigations.