I never saw LEXX, though, is it worth the effort?
Depends on what you like, LEXX is more risque, more semi-pornographic, and a lot more fun .
The concepts you mentioned for Serenity sound similar to LEXX, but not the same thing ofcourse . .
I liked the second-to-last season of LEXX the best, when the redhead who played Xev was all lips, hips, and dead-sexy. The crackhead-looking Xev from the last season, not so much.