Factory wheels with aftermarket lug nuts.
 

Is it possible to use aftermarket lugs on our factory wheels? I searched and couldnt find an answer. Thanks for your help.

nope

Actualy, assuming this is like all other Subies, they will work. Every Subaru I've owned has used 60* conical seat wheels, which is the same taper as almost every aftermarket wheel/lug.

In my experience, aftermarket lugs on stock Subie wheels: fine.
Stock lugs on aftermarket wheels: Usually not fine (lug head contacts wheel mating surface)