The short answer
List the target markets and intended use early. The project plan should identify the necessary reviews, testing work, documentation and the party responsible for each step.
In more detail
Radio functions, batteries, materials and the operating environment can affect the required assessment. Pre-compliance checks can help find issues while the design can still be changed.
Formal testing uses the agreed product configuration and the appropriate assessment route. A platform reference or a passed test on another model does not establish approval for a new product.