@Kray - Fate Grand Order was based on a smartphone game that required a bujillion servants to be summoned, so the story had to be flexible enough to handle that, thus resulting in a confusing mess, especially packed into one OAV.

Fate Apocrypha is a light novel series with two anti-heroes as main characters and two sides where a bunch of servants fight against the other party. It's different in a good way.

And there is a white-haired loli assassin.