How many careers are there in the film track? I think three (standard career, maybe with two paths, a part time career and one career for teenagers)... unfortunately it's not that clear from the simfans.de preview.
Well much like the Criminal or Police track or whatever in the base-game, there's two tracks in the film track. There's Actor, and Director. So when you get to level 7, I think, you get a choice depending on what your sim wants to be. Kids can act in movies, but it's only Teenagers that get part-time careers. There isn't any other careers for teenagers. Also, when you get past Level 7, you can choose weather you want to let journalists and the paparazzi into your household or not, which could be quite fun!
There's so much to Late Night, but acting and film directing and vampires and hot tubs and skyscrapers are high on my agenda.
Also, if you make a movie or act in one, it will be released at the Cinema. (Not the theatre, there's apparently and actual - well, more then one type - building for Movies specifically. So goodbye Theatre! (
However, you do get Theatres, and there's even a rumor about drive-in movies! Yay!)
Hope this helps.