I'm wondering where the Pre-Order goodies go when I pre-order the game. (I understand that the goodies most likely won't come until the game releases)

Will they just be dropped into some folder hiding away in the Cyberpunk 2077 directory folder?

Probably the same place where the regular GOG goodies go
If you are on Galaxy you can access your goodies for a game by clicking on the game in your library, then clicking on more next to play/install, then clicking on backup & goodies
Usually appears under game extras in this page (if there is no massive changes to the GUI for Galaxy before Cyberpunk ofc)

Funny you should call out the massive GUI change...
Just updated my Galaxy Launcher to the new version and the goodies section is gone (from what I can see).
I'll keep looking around the interface but has anybody already found it?

I am sure the goodies are there, where they are for other games.

Go to your games and click on a a game and you can download them. (Cyberpunk goodies @release)