The design-builder is often a general contractor with an architect on its team. Design and pricing happen together, so subcontractors often price before the drawings are complete.
Example: a design-build contractor gives a mechanical subcontractor a narrative and a floor plan. The subcontractor designs and prices the HVAC system.
Expect less detail and more responsibility. State your assumptions, your quality level and your exclusions in writing. Ask who carries design duties for your trade. Update your price at each design stage, and record what changed between stages.