your question is very large!
to have existing Splunk configuration you can use | rest command but it isn't easy to describe.
to have information about the indexed logs, you can schedule night searches and find results in the morning.
Maybe could be useful tu use some App like Distributed Management Console or other to find in apps.splunk.com.
Thanks a lot for this reference. Actually, my concerned about to know how many Indexer are configured in the network, count of source type or data source etc. Can we know those kind of information from the Splunk configuration?