GRS can be referred using the = operator. Mostly, we used to refer using datapages like =D_test.value. Dss is the one which we can set the values that can be changed at any point of time as these are just data instances.

GRS can have multiple instances based on env like for dev one value and for uat another value I think it is similar to application setting And DSS is that which we can give one value and it can be changed at any point and the use of dss in prod is important it does not contain any version so it can be change at any time