Hello folks! I've noticed some people have asked about compatibility with custom races on TTW, and so I figured I could write a quick guide as to how this all works from my experience. All custom race mods for NV seem to work fine on TTW. But you'd have to do some conversion and editing of any FO3 custom race mod. That being said, allow me to introduce some of the extra mods that may help if you are playing as a custom race.
First of all, this is ESSENTIAL for the ending of Fallout 3 in TTW if you are a custom race: Custom Race Ending Fix
It allows you to finish off the slideshow for Fallout 3 and continue into Broken Steel by getting rid of the slide that requires a race to be selected. You cannot continue as a custom race without this fix, so download it!
For those of you looking for the Children of the Wasteland mod, the one for NV works perfectly in TTW. My only issue playing with this race has been occasionally... falling through floors, but this bug exists in vanilla as well and is fixed upon closing out and reloading the game. You may also be interested in its companion mod, the Lutana CotW Expansion, which adds several features and makes use of the MCM menu mod.
The only caveat I've encountered with the Child race is that you are not tall enough to reach the controls at Project Purity, d'oh! Not to worry, download my hastily made mod that adds a movable milk crate to Project Purity for us short folks to stand on. For those who don't want to download a mod, use the console command tcl to enable noclipping, and float up a bit to reach the controls. Disable tcl afterwards, and you're good to go.
Any other errors you may have may be due to the mod itself, or need a fix from the Nexus for NV. If you really think you have an error with TTW, try a seperate, non-custom save file and see if the problem is recreated, and if so, tell everyone at the Report a Bug tracker. (See the sidebar to your left on any page on TTW's website.) I hope this little guide helps out!