Shadow Skill was originally a 2-part OVA 
(available through Manga Video).  The 
artwork is much better than the TV series, but 
the story is much more dis-jointed.  In terms of 
getting a fully developed story, I definitely 
recommend the TV series.  Although I began 
watching the TV series because of the OVA 
series.  I believe that the OVA series does 
contain better fight scenes, artwork, and (yes) 
fan service (although it's been years since I 
last watched it).

The OVA character designer was Shin Matsuo, and 
it was created (I think) by Metake Okada.

Oppose Ele as a main character is her pupil, Gau.

As for BtX, the character designer was Shingo 
Araki, most famous for Saint Seiya.