7.4.1 Purchasing process
The organization shall ensure that purchased product conforms to specified purchase requirements. The type and extent of control applied to the supplier and the purchased product shall be dependent upon the effect of the purchased product on subsequent product realization or the final product.
The organization shall evaluate and select suppliers based on their ability to supply product in accordance with the organization's requirements. Criteria for selection, evaluation and re-evaluation shall be established. Records of the results of evaluations and any necessary actions arising from the evaluation shall be maintained (see 4.2.4).
You establish the criteria, they can be different if you have different levels of suppliers as in your situation. I would surely have a different level if evaluation for a direct production material supplier than one that supplies off the shelf tooling items.
Again you seem to have answered your own question in your post.
By saying a supplier supplies less critical items you have carried out some form of evaluation.
Supplier evaluation could mean anything from supplier audits to questionnaires, or a simple desk top review of the supply, its criticality to the end product, and the supplier. From your evaluation you then decide what controls you put on your supplier.
What I mean by less critical is, the component is functionally less critical to the product to which this goes in. My question is, shall we say supplier evaluation (in terms of his system and technical capabilities) is not required.