Exactly. 168s/170s/171s can all be converted from/to each other, it's just coupler differences (168s/170s have different electrical wiring of the BSI couplers, while 171s have Dellner couplers).
Though Clubman preceded Turbostar in terms of the known name, Clubman continued to be used as an operator brand by Chiltern for the Class 168 Turbostars (like how the First Great Western 180s were Adelantes even though they were Coradia 1000s).
168s/170s/171s are all considered Turbostars. As for the different cabs of the 168/0s, I've heard two things. 1) The cab design wasn't finalised and 2) Chiltern wanted them to look more like the 165s, but then didn't bother with that from 168/1 onwards, ordering them with the standard "170" cabs.