I am very familiar with modded Morrowind, Oblivion and Skyrim.

What I am curious about is whether there is anything I should know, that is specific to modded Fallout 3.

For example, is Wrye Bash as useful and reliable as it is for Oblivion and Skyrim? If not, what should I use instead, or as well? FOMM?

I have installed FOSE and BOSS already, because I suspect they will be vital. It seems that the Unofficial Patch is not necessarily so, which is interesting...

IIf I were to use MMM and FWE, what else meshes well and makes sense to go with them?

Really, any suggestions, or warnings about tricks, traps, bugs and so on, will be appreciated. Thank you!

This may be my opinion, but I think I am right when I say: Oblivion and Fallout 3 don't have memory leaks, they ARE the memory leaks.

You want:
Wrye Bash
FO3Edit
Fake Fullscreen so you can play windowed without windows borders
Fallout 3 Stutter Remover
Unofficial Patch ( apply this change to Unofficial Patch - Broken Steel http://forums.nexusmods.com/index.php?showtopic=401813 )
Fallout Remastered ( disobey the author's directions and apply that same change to it http://forums.nexusmods.com/index.php?showtopic=401813 )
^These two are to prevent that infamous Rivet City save crash
Some form of Purge Cell Buffer ( be aware that this can cause instability, it should be one of your first suspects with crashes and freezes )
D3DOverrider because FO3 does not use triple buffering. D3DOverrider is part of RivaTuner http://www.guru3d.com/category/rivatuner/
Large Address Aware Enabler
Apply this to your .ini http://fallout3.nexusmods.com/mods/7529

If you are religious, pray. Pagan, do magic. Athiest, ask more help on these boards or convert to religion.

Also, since you are using MMM which increases spawns I recommend putting your ugridstoload to 3 instead of 5. Worth it to prevent slowdown in spawn heavy areas. There is a special procedure to do this, you cannot just make the change to your .ini and expect your game to load. First, load your game. Alt+Tab out of the game and make the change to the .ini in your MyGames/Fallout3/ folder and save it. Go back to your game and use console

refini

Then save your game. Exit. Restart game. Load that save and play. You probably know this already.

Edit:
iirc, FWE makes guns very loud, so try this
http://fallout3.nexusmods.com/mods/17445

For FWE + MMM, don't be afraid to ask advice and read up on FOIP patches and which FWE / MMM modules to use and which ones NOT ( important ) to use.
http://fallout3.nexusmods.com/mods/4968

Do not try to use FOOK2 with FWE.