I set the game to not update automatically and I know that means it'll only update if I launch it through Steam. That didn't work though. It just forcibly downloaded the update when I launched it with F4SE. I canceled it before it could finish, but it was almost done. I'm not sure if that may have potentially damaged my game or not, but this shouldn't have happened since I specifically have it set to not automatically update. Has anyone else had this issue before?

Edit: I think this partially downloaded update damaged my game. All my settlers are no unassigned and won't stay assigned when I put them to work and now all merchants have 0 caps. No idea what to do.

i believe i had the same problem, most of my mods that i had which require them game to be the same versions as the mods broke and dont work like for example looksmenu and the Mod Configuration Menu mods. i dont think Bethesda updated anything other then the creation club

The update, if I remember correctly, only fixes a few issues with Creation Club. It also changes some coding so the game won't conflict with the F4SE and your load order, but reading OP's clearly mucked up something in the game. Kind of a big middle finger to us when there are plenty of bugs to be fixed in the game and they only fix Creation Club. How about remove that bug you potato faced asshats.

you can easily switch to an older build for any steam game with the steam dev console when needed

you should:
a. set auto-update timer to early morning such as 4 a.m.

if you're using F4SE, instead of launching from steam launch the game through F4SE executable as it will not trigger the steam update.

EDIT: sorry for not reading your post entirely...and it's weird that F4SE actually triggers the update. I always launch F4SE via NMM without issue.

as an additional information, F4SE and its plugins work like a patch -- a patch at run-time to be frank. This means that they involve hooking/changing flags/changing data from a particular memory address(es), and that they'll need to pinpoint the address correctly. if not mistaken, usually it is done through dll injection (well probably that is why all F4SE mods have dlls to be injected by F4SE). when an update rolls out the memory addresses are possibly "re-rolled" (not sure if it's the correct term), so when F4SE or mod depends on it retrieves a wrong/empty memory address, it breaks.

Before I start playing Fallout 4 I always put Steam in offline-mode to have more control over potential Updates.

Yea that almost happened to me when i selected it in Steam instead of the script extender version but i smashed the pause download button, but now i have "Fallout 4 -Update Paused" forever in my steam library which has been annoying me. But honestly I think you should just finish the update to fix your game and just ignore the Creation Club stuff. Mine hasn't ever forcibly download before though to answer ya question.

Mine hasn't updated. It says update required but won't download unless I tell it to. Supposedly the newer updates after this will no longer break F4SE or any other mods, though their track record doesn't inspire much hope

F4SE's been updated again, but I still can't get past the black screen before a CTD. Is it the same for everyone or is it an issue regarding my mods? Can't tell most times

then set f04 to an older build with the steam console. that´s it

here´s a quick tutorial:
- rightclick on steam desktop shortcut, click properties and add -console after steam target address
- go to steamdb.info and search your game
- get game/app id number
- get depot id number
- get manifest id number
- Download the package

download_depot AppID, DepotID and ManifestID

for example:
download_depot 377160 2261566 7417123819347697483

- not all games built on single depot
- the package download will be on your [path to steam folder]/steam/steamapps/content folder
- replace the game files and prevent steam from auto updating