Windows 10 speedup and debloat

https://malwaretips.com/threads/how-to-slim-windows-10-and-make-it-superfast.91924/

https://www.mirinsoft.com/download/cleanmgrplus/summary/11-cleanmgr/50-cleanmgr

Best Practices for File Associations
https://docs.microsoft.com/en-us/previous-versions/windows/desktop/legacy/cc144156(v=vs.85)?redirectedfrom=MSDN

File Types and File Associations
https://docs.microsoft.com/en-us/windows/win32/shell/fa-intro?redirectedfrom=MSDN

How File Associations Work
https://docs.microsoft.com/en-us/windows/win32/shell/fa-how-work?redirectedfrom=MSDN

That should be a decent primer for what you want to do. For further reading I suggest

• Best Practices for File Association
• File Types and File Association, especially
• How File Associations Work

And see also my similar answer to a similar question:

• Associating file extensions with a program