Proposed plans are typically used during the project planning stages and may be (for example) sent around to various entities, colleagues, or departments, etc for their comments on the plan. They may comment on how the proposed project plan affects their infrastructure or operations for example or to provide further expertise or background knowledge etc. Proposed plans may also be used for detailed budgeting and funding securement, and for approvals from supervisors, managers, or even council (if in a municipality setting).
Construction plans could be the "Issued For Construction" set and are as final as can be based on the existing planning and knowledge of the project. The Construction Plan is typically also approved and stamped by the engineer as compared to the proposed plan which would not be stamped yet. For many, the Issued For Construction plans are used for the tender/bidding process.
