You should find all neccessary information about Splunk TAs and the kv store in your "_internal" index.
As a second step you could check the "source" field for the TAs that you want to monitor. Most of the available TAs are writing logs in their own logfile under $SPLUNK_HOME/var/log/splunk.
For the kv store check the mongod.log.
More information:
What Splunk software logs about itself - Splunk Documentation
