Board Thread:Questions and Answers/@comment-39.50.41.25-20190216192110/@comment-3180631-20190216200756

Steam version should be identical to downloaded RTP version, although Steam itself provides an extra bonus of cloud storage of save files (probably).

As far as I can tell, the DLC doesn't modify the game, it's only there to let people pay respects as well as permanently add the game to their library (Steam technicalities).