SSIS connection used based on passed value
You want to incorporate Environment Variables into your SSIS Packages. Setup the agent job to use different environment variables. 

You can set the variables at each step in your agent job. If you create multiple SSISDB Environments in your project folder they can be use or store different variables for executing your SSIS Packages. 

Reference: 
https://www.mssqltips.com/sqlservertip/4810/setup-environment-variables-in-sql-server-integration-services/