FIrst of all, if you observed different results when different displacements are used in a Displacement boundary condition, can you look at End Time in Analysis Settings? Is the End Time the same between these two analyses? If yes, velocity resulted from the Displacement BC is different. It is possible to observe different material behavior if the materials have different velocity and thus result in different dynamic response.
It is OK to pull material properties from different sources and then use them in Explicit Dynamics system. If you want to model "fracture" as mentioned in your post, you need to make sure Failure Model is included in the material properties. When Failure Model is included, material will fail (fracture) when stress/strain has reached its maximum value. This is very critical to get the accurate representation of the material behavior. Failure model can be added from Toolbox in Engineering Data.
The default contact type is set to Bonded if the distance between material interfaces is within the pre-defined tolerance. You need to check each automatically-created contact region to make sure they are needed and represent the actual motion occured at the material interfaces. If you are trying to model the 3D printing and the new layer of a resin material is printed and settled on the existing material, bonded contact is the reasonable representation of the connections.
If the materials in your model donot include any plasticity and just have linear elastic material properties, the material behaves elastically only. Its plastic strain is zero. If you add material plasticity and failure model to the materials, you should be able to observe non-zero plastic strain and material failure if the resulted stress/strain is high enough.
To plot plastic strain, the user-defined results Effective Plastic Strain is the more appropriate variable to use, since it is the one used by Explicit Dynamics solver. Equivalent plastic strain is primarily used for MAPDL solver in other Mechanical Analyses such as Static Structural & Transient Structural analyses.