Extensions removal

You let Big Sur handle it. You can give permission to use some per this Apple article:

About system extensions and macOS - Apple Support

Removing extensions on a whim can result in a not-working computer. Ultimately, it is the responsibility of software developers to react to OS changes. All you ,the end users, can do is encourage a non-conforming developer to get with the program.

If you mean Safari extensions:

1. Open Safari
2. Click the Safari menu
3. Click Preferences
4. Click the Extensions tab at the top
5. Uncheck any extension you no longer desire