Actually, the reverse is generally true - the more expensive cases (DW, Yuki, NDtrading, etc), having been designed to gen specs, tend to be the same, whereas cheap copies, being less concerned with dimensional accuracy, tend to vary.
I agree with Nanuq, since we know nothing about the parts you have, it is impossible to tell whether or how they will fit together. So your best option is to dive right in & find out. Then report back with good, clear pics.