Can I go from a parallel crease to a tapered crease? (photos)

You had an acceptable result following the upper blepharoplasty. The risks of improving the arch of your crease are far greater than the benefits you would achieve. In your situation pursuing a better crease may lead to a complication. I hope you find this helpful. 

Yes, it can be corrected. Make a small crease below the current parallel crease and remove the skin between two creases, so you will not get two separated crease afterward. Also your crease have quite thick muscle under the skin which sometimes patients called this as sausage crease can be corrected by removing the muscle under  skin.

There are many types of naturally occurring "Asian" creases in the Asian/Southeast Asian ethnicity. I agree with you that the tapered crease is a more commonly accepted type of crease.With a revision lid crease surgery this could be achieved, though there is always a risk of visible scar and/or multiple crease formation.I would recommend seeing an Oculoplastics surgeon with experience in Asian blepharoplasty.