There are just things you cannot do while moving. So the ideal would be having 3 different workstations. One where you can sit. One where you can stand and one where you can lie down. Alternating between them. As for movement I recommend taking breaks / walks. Much healthier and productive.
This is not ideal if you stay in this 8h per day. There is no right posture, the ideal for your body is movement. Let's think about products where you can change your posture during the day and still use your computer :)
