Yes, it certainly depends on subtype. As my self-typing is INTj-INFp my Ni(8), Fe(5) and Fi(3) are certainly stronger than those of an average INTj.
8 > 1 > 2 > 3 > 7 > 5 > 6 > 4 should be the correct order for me.
might be an unusual order of function strength for an INTj - but subtypes play an important role...