Please forgive a GOG relative newbie for the following question which has assumedly been asked and answered before:

Do enhanced editions of older games include an option to play the original 'un-enhanced' version, for those who want to re-experience it just as it was, or are these updated editions strictly....well...updated?

It really depends on which game. The Baulder's Gate games were originally the standard version, then the enhanced versions released and they dropped the standard, but they again, after many requests, added the standard version to everyone's account that has the enhanced version.

Most games come with the base game and then any addons or DLC are downloadable separate, but not all of them. What games are you referring to? I may have them in my library and be able to tell you if the original game is included.

https://www.gog.com/forum/general/bonus_games_included_in_gog_games

Thanks...

- Icewind Dale...?
- Planescape Torment...?
- The (first) Witcher...?

I believe the two Beamdog EE games should come with the old editions in some form (they used to, at least). They were separate items in the library, though. But I own neither of those Enhanced Editions, so I'll let someone else give advice on those.
EDIT: Actually, I think Planescape: Torment EE has a setting that will turn off most of the added convenience features and such, and let the player have a "pseudo-classic" experience within the remaster. But it should also add the old Hasbro-published version to your account as a separate item, as mentioned above.

The Witcher: Enhanced Edition Director's Cut (they chopped off the last bit of the title, which apparently just meant that it's the uncensored version, but the game itself hasn't changed since) isn't a remaster; it's just the patched, fixed version of the rather buggy original, with a bunch of added stuff -- some extra adventure modules (some fan-made) that are accessible from the main menu, a crapload of out-of-game downloadable bonus goodies, and maybe some improved in-game options and additional supported languages or something. There's no way to play the less-patched earlier version from this digital copy, but I can scarcely imagine many people wanting to.

Thanks for each of the replies. I appreciate your time and comments.