The current Aga Khanis or followers of Aga Khan, if they are even religious, have mostly adopted the Sunni fundamentals. But you can still find some of his followers who still holds Ali (as) in high regards and deemed him as the rightful heir to the Holy Prophet (pbuh). But it is hard to figure out what their religious belief is in the 20th and 21th century because most of them or a very significant number of them are very secular. Even the Aga Khan and his family do not appear to be holding to some of the traditional Islamic values that are heavily emphasized in Islam.
Their practices are quite different, not only from us, the Shia, but also from other Muslims. I remember seeing a cultural video of them performing arts and dances wondering if they have been heavily influenced by the cultural aspect of other religion.
I don't know what you mean by they are claiming themselves as being Shia? We don't really consider anyone other than us as Shia. Unfortunately, we cannot stop people using the label Shia.
