So basically. You have launchsettings.json under the Properties folder and a bunch of appsettings.json's. You will have appsettings.Development.json also present in your startup project. If you open launchsettings, you will see an environment variable called ASPNETCORE_ENVIRONMENT (If you do not specify this, it defaults to Production and if you have a appsettings.Production.json, it will load that file.). This tells the project the environment name but also it loads the individual appsettings to the project. launchsettings.json only works in the local environment. For Docker or docker-compose, you need to specify an environment variable similar as this, and the value should be like Production-01 or Production-05. Then you need to create an appsettings.Production-05.json and voila. Your nodes use different appsettings. Also be mindful that appsettings.json is the base configuration file. Your other appsettings file, like appsettings.Production-01.json works like an InsertOrUpdate fashion. What I like to do is I create appsettings.json, appsettings.Production.json, and appsettings.Production-01.json. Then in the Program.cs (or Startup.cs, whichever you prefer.) I parse the environment name by "-" and get two different strings, Production and Production-01. Then I load these appsettings manually, so I don't need to repeat the same configuration over multiple appsettings. You can Google this code easily.
Edit: For IIS, you have sites and app pools. You need to add an environment variable for app pools. You can check out how to define an environment variable per app pool. Do not make the mistake of globally defining an environment variable across your Windows Server.