Splunk provides three different search modes: Smart, Fast, and Verbose. 'Smart' mode optimizes search speed and accuracy by dynamically adjusting settings based on the job. 'Fast' mode prioritizes search speed over completeness, returning results faster but with minimal field discovery. 'Verbose' mode ensures all available fields and data are processed, trading off speed for comprehensive results. 'Automatic' is not a recognized search mode in Splunk.