Double dreadlocks have more volume.
For whole head you need: Dreads, Dreads+Braids, Dreads+Braids+curls - 45-50 double OR 70-80 single. Curls only - 50-60 double OR 80-95 single.
Thick hair (no matter type of hairstyle) - 55-60 double or 90-100 single.
Mohawk/undercut/partial installation - YOU CAN SEE IN THE PICTURES