Blocks can be modeled using joint elements or material boundaries. How the blocks are treated by RS2 depends on the method used.
In order for the blocks to be considered separately, they must be separated with joint elements. The RS2 Joint Network Verification document provides examples of how to create distinct blocks. Note that you’ll also need to define the strength properties for the joints in order to model slip between the blocks. If only material boundaries are used to separate the blocks, they will behave as a continuum.
In terms of modeling the interface, either material blocks or liners can be used. If you are interested in flexural failure and moments, the liner elements are preferable. Note that if you are interested in modeling distinct blocks then material blocks will have to be used. If the wall is acting as a unit, without slip between the blocks, a liner may be preferable.