When I turned on my computer a few minutes ago there was an automatic update in progress for "GOG". My question is: Will the update aotumatically apply itself to my game "Grim Dawn" or will I have to do something to match the GOG update to Grim Dawn? Thank you!

You need to d/load update and install it yourself.If using Galaxy,no idea.

Galaxy automatically downloads and applies updates, if the automatic game update is not disabled. Judging by your post, you seem to have the default settings: enabled
If automatic game update would be disabled, any patch would not be downloaded. When you manually tell Galaxy to update the game because it told you that an update is available, the update would fist be downloaded and then applied without further action on your part.

Galaxy updates do not affect the games directly. The game updates are separate and can be downloaded automagically by Galaxy if a new game update is released.