The description you provide addresses conforming clothing and associated morphs, if there are any available.  Those are inherent to the clothing as the vendor has provided, and you are pretty much bound by those (no pun intended).  However, you can modify those morphs by using the morph brush tool within Poser to make either subtle or drastic changes to the mesh.  Magnetics is another option.  Even taking the clothing object into a 3rd party modelling program could yield better results provided that vertices and mesh are not changed or severely altered.

Dynamic clothing is different, you need to enter the cloth room to apply such clothing to your model, but there is a lesser degree of having it drape as you would like.  The more complex the posing setup, the more frustrating it will be to get the desired results.