Saves are not compatible between the original release of D2:ED and DKS / D2:DC (there were too many changes made when D2:ED was remastered). A DKS save should be fine in D2:DC, though at least if DKS is not patched (not an issue for the Steam version) it would have a problem with D2:DC saves (though if you have D2:DC there isn't much point to switching to DKS).
The DRM was removed already from the Steam version of DKS, and there was never any DRM in D2:DC.
