So who are the mod experts here?
I just one simple question. For a test I need to run the game just once without any mods.
I installed them all properly with Vortex (Program from NexusMods).
I now just want to start the game once without mods and then just easily start it with mods.
I dont want to disable them one by one in Vortex which could mess up something.

Any ideas?

I think the simplest way to do that would be to do a second, clean install of the game on a different location.

That's what I did when I was testing various CP77 mods and installing new patches.

How do you install the game at a different location if you got it on gog?

Simple. When using the offline installer - which I'm always doing, I don't even have GoG Galaxy installed - you can choose the install path on the second screen of the installer.

You select language to proceed with the install, and then click on Options on the bottom-left.

Though as you've already got the game installed, it may not work as the installer could think you're trying to update the game. In that case, you'll have to copy-paste the whole install directory. Which is again how I have done it. And then remove any mods manually to get the game set up the way you want it.

I got a ton of mods too, to the point where I've completely lost track, but I've installed all of them manually and haven't tried Vortex. In the case of several mods, I read on Nexusmods it's recommended to do it manually as Vortex tended to screw something up.

I've been trying to play this game through gog for days and I haven't even gotten past the loading screen. Is there a guide or something I call follow so I can use the backup installers to actually play the game.

Then you must have done something wrong, because I have kept the same game install since release patch 1.03, and just patched the game manually as necessary. Currently on patch 1.6 due to all the mods I have installed.

I don't know the Visual C++ redistributables requirements for CP77, but have you checked which VC++ versions you have installed?
https://support.cdprojektred.com/en/cyberpunk/pc/sp-technical/issue/1568/the-game-is-not-launching-5

Only other game where I had the issue of always crashing after the intro logo was Black Mesa, where I was missing a single x86 VC++ install.

Tried reinstalling your graphics drivers and done a CLEAN install? Tried installing an older version of the game? If you don't have the offline game installers back from patch 1.5 or something, you'll need to find yourself a torrent to get them.

I got the original 1.03 files + every patch since on my home server. From all the issues I read about this game, it's apparently 315 GB well spent...