Hello Vjdavis,
It sounds like you lost some functionality of your mouse and trackpad after updating to Big Sur. We understand how important this is for your and we're here to help.
First, let's verify the settings are correct using this article: Change mouse tracking, double-click, and scrolling speed on Mac
If the issue persists, test in a new user account using this article: Set up users, guests, and groups on Mac
If you are still having functionality issues, can you provide a few more details? Have you tested with an external mouse or trackpad? Did you notice this issue as soon as you updated your Mac? Also, have you experienced any trackpad or mouse issues prior to updating?
Cheers!