This setup takes just a few minutes, is easy to do and works 100% with no issues on my system:
i9-9900K @ 5GH / 1080ti 11GB / 32GB Ram
SamSung SSD for games / SamSung m2 for OS
Windows 10 64bit Pro - 4k 75" screen

- Attempt game launch first and install all needed redist from Steam
* When game option launcher appears turn off anti-aliasing and anisotropic filtering
* Go to advanced and turn off transparency multisampling
* Can set to 4k res (so far)
* Now go to the "DATA FILES" below "OPTIONS" on the launcher window and put a check mark next to all the DLC pieces

- Close everything

- Install the XLIVEREDIST.MSI in the gfwlivesetup.zip first
* https://community.pcgamingwiki.com/files/file/1012-microsoft-games-for-windows-live/

- Install Fallout3_1.7 update
* https://patches.bethsoft.com/fallout3-patchnotes-1.7-en.htm
* Game should launch
* If it doesn't you may have to copy xlive.dll from windows\syswow64 to windows\system32 and try again
***NOTE***If Fallou3_1.7 update still fails you may need to install GFWLIVESEUP.exe from the below link
* http://go.microsoft.com/fwlink/?LinkId=128962

- Close and continue to tweak

- Enable multi core threading & disable mouse accelaration
* Open Documents\My Games\Fallout3
* Edit the newly created FALLOUT.ini
* CTRL+F "sLanguage=ENGLISH"
* Add these two lines just below the english line
bUseThreadedAI=1
iNumHWThreads=2
* CTRL_F "controls"
* Add these lines just below the "bBackground Keyboard=1"
fForegroundMouseAccelBase=0
fForegroundMouseAccelTop=0
fForegroundMouseBase=0
fForegroundMouseMult=0
* Save and close

- Use GFX app to force anti-aliasing and FPS cap to prevent issues in the game with crashing or incorrect physics
- Open nVidia control panel>Manage 3D settings>Program Settings Tab
* Select Fallout 3 (fallout3.exe)
* Antialiasing - FXAA - ON
* Antialiasing - Mode - Override any application setting
* Antialiasing - Setting - 4x
* Antialiasing - Transperencey - (Should be set to global 4x)
* Max Frame Rate - 60 FPS (Needed to keep physics in check)