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Begin with the question
Running out of storage, a busy startup, and a slow application are different problems. Review the available storage and resource observations before choosing a cleanup or settings change.
Choose cleanup categories deliberately
Temporary files, browser cache, browser history, cookies, and download records have different effects. Removing download history need not remove the downloaded files; clearing cookies can sign you out of websites.
Review startup without uninstalling
A supported startup registration controls when an application launches. Disabling that registration is different from removing the application. Keep a record of the original state and the reason for the change.
Know the recovery boundary
Supported registry, startup, shortcut, and settings changes can retain originals. Temporary-file and cache deletion generally do not have an application Restore option. Review the scope before confirming cleanup.
Treat diagnostics as observations
A short performance sample can help identify high resource use, but it does not establish every cause of a slowdown. Cleanup and registry maintenance do not guarantee a faster computer.