Check the Plus+Disc. Anyway, basically, Shiki becomes close with Satsuki, and realises she's been living a lonely life ever since she became a vampire. It seems that, at some point, Satsuki started to struggle against her vampiric impulses.
I already mentioned Nrvnqsr and Roa team up in her route. I do not know much besides that.
There was a bit about her becoming really beautiful once she becomes a vampire (I did not understand what they meant with that, since she was already one in Tsukihime and there was no big difference. Perhaps they meant she became a DA or a DAA?). It seems at some point her hair grows longer (this is one of the features defined as beautiful).
MB is follows Satsuki's Normal Ending (I do not have the source for this but, it's pretty well known Nasu said it). In MB, Shiki is with Arc, and Satsuki is alone. So, we can assume her Normal End is a sad one.>>9453974
I wouldn't know, I just didn't. I'd say it is a matter of tastes.