if you have drainage either weep holes or a perforated pipe then granular backfill would be preferred.
If you are only compacting a small width of backfill behind your wall then granular would again be better since its easier to work with and compact in smaller areas.
Cohesive fill maybe better if you want to reduce the potential for ingress of water into your basement wall.
Your Geotechnical Consultant should have given you active, passive and at rest pressures on this wall. What did they base these loads on? In other words, his/her design, his/her backfill guidance.
There could be a metre thick at the top... The backfill space is generally what is required for construction of the foundation wall. They normally replace the excavated soil with clean backfill. I also use Miradrain with foundation walls. and an impervious clay cap and topsoil (we have lots of clay) to cover the granular fill.
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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates