When using Project Mode, various settings are available to control the features of synthesis and implementation. These settings are passed to runs using run strategies, which you set in the Settings dialog box. A run strategy is simply a saved set of run configuration parameters. Xilinx supplies several pre-defined run strategies for running synthesis and implementation, or you can apply custom run settings. In addition, you can use separate constraint sets for synthesis and implementation.
For information on modifying settings, see this link to the Vivado Design Suite User Guide: Synthesis (UG901) and see this link in the Vivado Design Suite User Guide: Implementation (UG904).