Is the Season 1 Christmas special stand alone, or is it part of Season 1? And what's the difference between the Steam version of Season 2 and the regular version?
If you downloaded the 5.4 Gigs for Season 1, the Christmas Special is included.
At some point it was available separatly, but I never tried that one. It's very likely stand alone.
There is no "regular" version.
First only the Patreon (I think) version was available, then Steam and a day later GOG were uploaded (version 1.0.3).
Steam and GOG are both the same basically. Maybe they have a different logo, but that's about it.
The story content in both is complete, but both lack full voice overs, that will be added in the upcoming months.
If they now add the four or five missing voice files to Season 1 on GOG, so the errors won't appear anymore, I'll be a happy customer.