I've been having the same problems here since upgrading to Big Sur. Finder freezes, programs freeze and lag (sat on the color wheel for almost 9 minutes the other night before I had to force a shutdown). I've never had an issue with Apple products like this before.
I'm in Adobe programs all day and it's maddening. Hoping this gets fixed soon as I am absolutely losing my mind trying to work.
MacBook Pro (16-inch, 2019)
2.4 GHz 8-Core Intel Core i9
64 GB 2667 MHz DDR4
AMD Radeon Pro 5500M 8 GB