It is our experience that the MTP trained on crystal displacements alone is sufficient, and can describe crystals in MD at moderate temperatures very well without active learning in almost all cases.
If you are unsure, you could run some MTP simulations of small systems, check that the simulation runs stable, and compare the forces from MTP with forces from DFT on a few snapshots from this simulations. The error should be similar to the training / testing error of the MTP.
