You can actually roll back versions on steam.
To do so, right click on Neverwinter Nights: Enhanced Edition in your steam library. Select "Properties...". A new window opens where you have to switch to the "BETAS" tab. There you can select a build of your choice. GOG is still using Build 8186 (v1.78). Not sure about the builds in between as I am using the GOG version for Layo.
Hope this helps!