Hi
indexer stores the data onto disk. There are couple of different formats which can used. See e.g. https://docs.splunk.com/Documentation/Splunk/8.2.0/Indexer/HowSplunkstoresindexes
yes all those formats are supported see more https://docs.splunk.com/Documentation/Splunk/8.2.0/Data/WhatSplunkcanmonitor
r. Ismo