the off line installs are Gog... they make them and control them
yes Gog Galaxy has the correct build
Yes, I cannot comprehend why people still use the manual files. The myth is that if you use Galaxy, then you have to run the game through Galaxy. Nope. You can run all Galaxy installed games right from their own exes, bypassing Galaxy completely. No DRM means No DRM, whether you use Galaxy for installing and updating or you don't...;)
Galaxy has been out of beta for years now, and it works great, and game updates come much quicker through Galaxy than having to wait on Gog to take the developer's patch and wrap it up in an exe inside the manual files. With Galaxy, just like Steam, the dev can load in his patch himself--and Gog isn't involved. And sometimes with manual files, depending on the update, Gog may make you download the entire game again!...;) I only use the manual install files after a game has received its FINAL PATCH, and the manual files serve as my own archived copy of the installable game for my library. Seems to me that's
the purpose of the manual install files. Galaxy is a huge improvement over the time when Gog offered nothing but the manual files, which always got the game patches late.