How to optimize a long-used Windows 11 install without a reset

[ZacharyKW]

I've been using the same Windows 11 installation on my primary work laptop for over two years, and it's gradually become sluggish with long boot times and noticeable lag when switching between applications like the Adobe suite and multiple browser tabs. I've run the basic disk cleanup and disabled some startup programs, but I'm hesitant to do a full reset and lose my configured development environment. For power users who maintain their systems long-term, what are the deeper Windows performance optimization steps you take that go beyond the surface-level tips? Are there specific built-in tools like the Performance Monitor or PowerShell scripts you rely on to diagnose bottlenecks, and what third-party utilities, if any, have proven safe and effective for cleaning registry entries or managing background services without breaking things?