<<Can anyone give me a listing of the various dll files and drivers and how they are using them?>>
Why do you want this? The installation takes care of all the DLLs. I certainly hope you aren't planning on installing the DLLs yourself. To quote a phrase, "There are no user serviceable part inside."
<<From what I have obtained so far the Data Manager driver would be used by Designer for DSN access to the catalog, but you are also able to select the Data Client, Data Client for ADO, Relativity DBA, and Data Server in the Designer product.>>
The Data Manager accesses a single-tier data source, that is one in which the data is on the same machine as the ODBC application.
The Data Client and the Data Client for ADO access a client/server data source, that is one in which the data is on a different machine from the ODBC application. This configuration, of course, requires that a Data Server be installed on the machine with the data.
You can not access the Relativity DBA or Data Server directly from the Designer, at least not as a driver. (It is true that, is the Data Server is installed on a Windows machine, a Relativity Data Server driver appears in the list of ODBC drivers, but this is for creating Server Data Sources directly on the Windows machine without using the Server Administrator. It is NOT intended to be used for data access.
<<If I understand correctly the Data Client for ADO is used in SQL linked servers and also for other Visual Studio projects that need to access the Cobol data.>>
ADO is a database interface that Microsoft developed to replace ODBC, but it never did replace ODBC. ADO has the ability to connect to an ODBC data source under the covers, allowing an ADO application to still access ODBC drivers, like Relativity. Unfortunately, while ADO to ODBC connection works, it seems to work best with other Microsoft ODBC drivers. The ADO version of Relativity was introduced to work better with applications using ADO.
<<Is that correct and what about the other drivers>>
The only other real driver is the Data Manager, and it also has an ADO version. The Data Server driver does NOT have an ADO version. Use the Data Client one instead.
<<Also I am working with another developer to have connection strings into the catalog - since I set up the DSN using the Data Client for ADO does that mean they need to use one of the dll files under Relativity Data Client folder?>>
I have no idea what you're asking about here. What are you trying to accomplish? Please don't worry about the DLL's.
At lot of this is described in the Release Notes. Please read them.