In the Beginning is like fanfiction in that it's backstory (and post-story) which makes no sense to anyone not familiar with the show but very watchable for fans. (The other movies you can skip.) The scenes with old Londo are sad but not without hope; he's still himself, and while he breaks my heart with one particular statement, I find it oddly soothing that in the last hours of his life, he found the time to tell children a story and flirt a bit with their pretty nurse while waiting for the right time to get drunk in order to release Sheridan & Delenn. (Also, as indicated in the script, the children are grandchildren of Urza, his old friend, because Londo kept his promise to take care of Urza's family.)

Re: Emperor Turhan and the implications for Londo, my other bit of fanon concerns Londo's nephew Karn who is important in the first episode of season 1, Midnight on the Firing Line, and never referenced again, which is rare because JMS is really good with continuity. Considering what Karn is made to do in that episode and considering, again, the Romans as model, my fanon is that Karn more or less is forced to commit suicide afterwards, which in combination with the fact that during s1 Londo is directed to concede during every Narn/Centauri confrontation (notably in the s1 finale) contributes to House Mollari's low standing and Londo's growing bitterness towards Turhan's policies and willingness to join Refa's faction.