I felt that the number system was right but I never thought that, excluding Aizen and troup, there was always stronger arrancars. I guessed Wonderweice but I still think he isn't perfect cause he's borderline down syndrome.
Honestly looking forward to Kensei's fight. I think he's the strongest aside from Shinji. Hiyori is probably comparatively weak to the other vizards.
As for unique abilities they all probably have something along the sort. Ichigo's is huge stamina and rejuvenation. His stamina was high to begin with but I think his hollow side kicks it up a lot and thats why he can rejuvenate fast as well. They all took it as a surprise.