Themes is jazz hybrid? Perdition City is acid jazz? Perdition City has some smooth jazz influence... but Themes has nothing to do with jazz and Perdition City isn't acid jazz either. Way to steer someone in the wrong direction...
If you really want to know what they are, Themes is a mixture of trip hop, ambient, folk, and industrial on a metal backdrop while Perdition City is a mostly electronic soundscape style music with some jazz influence but far more idm influence.
I'd recommend that you go to the Ulver board and read up.