I've read about the use of Catalogs in 2012/14 SSIS as a replacement for Configurations in 2008. With that replacement, I haven't seen how people handled the scanario of a configuration that is used by all packages on the server such as a Server Connection or path location. With this scanario, all packages point to one configuration, and should something about that value change, all packages are updated. Is this possible with catalogs? It seems each project has their on catalog and if that is the case, everytime a server wide config / parameter changes, it needs to change in each project.
In the SSSIDB, a project lives under a folder. A folder may also contain an SSIS Environment.
When you right click on a project (or package) and select Configure, this is where you would apply configurations, much as you did in 2008. You can use an SSIS Environment that exists in the same folder as the projects, or you can reference one in a different folder. That is the approach I use and suggest to people.
In my Integration Services Catalog, I have a folder called "Configurations" (because it sorts higher than Settings). Within that, I create one Environment called "General". Many people like to make environments called Dev, Test, Prod but unless you have 1 SSIS server handling all of those, I find the complexity of getting my deployment scripts nice and generic to be much too painful.
I then deploy my projects to sanely named folders so the Sales folder contains projects like SalesLoadRaw, SalesLoadStaging, SalesLoadDW.
If I have created a new project, then I need to add a reference to Configurations.General collection and then associate the project item to the Environment item. For Connection Strings, you do not need to define a Variable to accept the string. You can directly assign to the properties of a connection manager (either project or package scoped).
The great thing about Configurations is that once you've assigned them, they persist through redeploys of the project.
The biggest thing that tends to bite people in the buttocks is that when you create an Environment and add those entries into them, DO NOT CLICK OK. Instead, click the Script button and script those to new window. Otherwise, you have to recreate all those entries for your dev/test/load/stage/production environments. I find it far cleaner to script once and then modify the values (SLSDEV to SLSPROD) versus trying to create them all by hand.