So I had Fallout New Vegas heavily modded to be in working, bugless, condition without the possibility of a crash. I used the Script Extneders and installed various mods and what not.

Any extensive guides to do the same for the GOG version of Fallout 3? I recall trying to get into Fallout 3 but then a crash happened while doing the Operation Anchorage DLC.

I haven't found an extensive guide for Fallout 3. There is less of that for Fallout 3, unfortunately. I think the best fixing mod is Stewie's tweaks. https://www.nexusmods.com/fallout3/mods/23561/

Well, this "mod" do a few things : https://www.nexusmods.com/fallout3/mods/21888/

So Fallout 3 as it is in its vanilla state is more stable then New Vegas?

I posted some stuff in the thread i did here:

https://www.gog.com/forum/fallout_series/here_are_some_good_fallout_3_modding_sources

This was true for me, but it might depend on what PC is being used.