User blog comment:RemosPendragon/Questions to ask/@comment-33731050-20150226092833/@comment-8395098-20150226174222

it's as easy as this, the Adeptus Mechanicus rules worlds and own starships. the people on those worlds are servents of the adeptus mechanicus, but they are not all tech-priests you have to be part of the Cult Mechanicus to be a tech-priest.

Skitarii, Princepts, and the bondsmen of Admech Starships all fall under the label of admech but do not belong to the cult mechanicus.

it's much like the old USSR, if you were Russian you were considered a "Communist" but you wern't actually part of the Boshlevek party.

and as for the ranks they can be found outside the FF books, some of the more sector specific ones not really, but all the Sister's of Battle rank titles, guardsman titles and arbite titles can be found in outside sources.