You've likely already bought it and played it a million times, but if you're wondering what Skunkape changed in The Devil's Playhouse remaster, look no further than this Steam post. The big improvements are outlined (higher resolution, improved lighting, Nutri-Specs on all platforms, and more) along with the per-episode changes.
Skunkape have also been hard at work patching the game post-launch, as this 1.3.0 update on Steam proves. No longer will Max be "scaled infinitely small if the player left a scene when Max was still shapeshifted via Rhinoplasty"... which frankly I hope to see reverted in the remaster of the remaster in a decade.