After much tweaking and reading, I ended up with a fairly stable game for my mods.

I can play for hours with only a couple of crashes, most of the time due to running while changing cells in busy areas (around DC).

What is stumping me is that, when I start the game after booting my machine, Fallout freezes the first time.
I have to kill the process and only then, the game can start up when I launch it again.

Very odd.

Did anyone experience something similar ?