Just upgraded to Big Sur and, among other issues, my Windows 10 VM flickers in full screen mode. It did not do this in Catalina using the same version of Fusion.

My system is 2019 15" Macbook Pro i9 with 32GB RAM.

In full screen my display flickers but not in windowed mode. My display is a Dell U3818DW running at 3840X1600. Again this worked yesterday before upgrading to Big Sur.