I think you definitely should learn Index semantics.
It works just like Vector for the most part, but is able to find index of element with given value really fast.
VectorMap is just a quite simple composition wrapper of Index and Vector. Index stores keys, Vector values.
Other than that, it really always behaves just like Vector.(Or two Vectors - imagine VectorMap as Vector<KEY> and Vector<VALUE>).
The only slightly problematic operation is Remove of element, not because it behaves differently than in Vector, but because it is slow (not only it has to move the memory, but also reindex hashtables). That is why there is Unlink that just "hides" the key, keeping the element in the place.