Since the GOG release already includes unofficial patches (at least the High Resolution Patch) and there are several Fallout 1 + 2 projects on the net, I'd like to know which of them gives the best Fallout experience.

There is for ex. Fallout CE, SFall, Fallout 2 Restoration Project, Fallout HQ music and many more.

I feel a bit lost.

Any recommendations?

Think of Et Tu (I think its also called FO1in2) as a QoL improvement. To me it's worth it and I believe it doesn't change anything in the storeline, but has some bug fixes maybe. It's been a while.

I think you can find YouTube videos of it. It's easier to see the improvments yourself rather than people trying to describe it in the commends. Nothing beats seeing a visual example of a mod. :)
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Thank you!

So, what I did for Fallout 1 if anyone has the same question:
1. I installed Fallout 1 and Fallout 2.
2. Downloaded FALLOUT ET TU (https://github.com/rotators/Fo1in2), sfall (https://github.com/sfall-team/sfall), Inventory Filter mod for Fallout 2 (https://github.com/rotators/InventoryFilter), High quality music for Fallout 1 and 2 (https://github.com/BGforgeNet/Fallout2-HQ-music) and Fallout 2 Restoration Project updated (https://github.com/BGforgeNet/Fallout2_Restoration_Project)
3. Made a new directory "Fallout1in2" in Fallout 2
4. Installed FALLOUT ET TU in the forementioned directory
5. Imported master.dat from Fallout 1 by using undat.exe
6. Updated sfall to the newest version (excluding ddraw.ini) overwriting existing files
7. Installed High quality music for Fallout 1 and 2 in Fallout1in2/data/sound/music overwriting existing files
8. Installed Inventory Filter mod for Fallout 2 in Fallout1in2/mods and added the mod to mods_order.txt
9. Tweaked ddraw.ini and f2_res.ini to my preferences

The first time you start Fallout, sfall will ask you if you want to disable the High resolution patch - I did choose yes

For Fallout 2 it's the same, exept instead of FALLOUT ET TU I installed Fallout 2 Restoration Project updated of course.

So far works flawless!