If we are practicing pranayam after yoga practice do we still need to do Shavasana? Should it be done after yoga or pranayam?

Yes, Shavasana is a must. If one has an intense asana practice, it is best to do Shavasana before moving to pranayama. This is to allow the heartbeat and breath to normalize. You can take a short second Shavasana after pranayama as well.

If the asana practice is light, then take Shavasana straight after pranayama.