The Hellsing anime has only 13 episodes, and is pretty different from the manga... The new ova's that are being released are supposed to be closer to the original manga history... 3 ova's have been released so far...
As far as I know the anime had only one opening... "Logos Naki World" by some dude called Yasushi Ishii... The ova's have a different one though...
"Visual Kei is a sort of glam-gothic-rock thing where the band might look like a space vampire who is also a gay Kabuki French countess.
That makes it sound better than it is."