Transmutation does not depend upon postures, but on wise use of energy. There are millions of students of yoga who use these postures but do not transmute energy or awaken consciousness, yet one can transmute energy perfectly well without using any of these postures.
At the same time, certain postures provide benefits when one is transmuting. Specifically, to transmute effectively, the spine and neck should be straight and relaxed, allowing all of the channels to flow freely.
Viparita Karani is a very powerful asana for transmutation. The instructions to use it are linked below.
Sarvangasana is a useful asana for health and flexibility. Swami Sivananda gives details in his book Kundalini Yoga.
In terms of effectiveness, all of the exercises we teach are effective. We teach them all because each person responds differently to them. It is recommended that you work with them all, giving each sufficient time that you become familiar with their effects, and thereafter you can best determine what is most effective for you.
Be advised that the chief factor in determining their effectiveness is your own use of energy from moment to moment, all day long, before, during, and after the exercises. If you are not learning how to save and manage your energy, none of these exercises will have any benefit for you.