We still haven't rolled out Big Sur to everyone. Originally it was because of a software compatibility issue but many of our test user group are reporting performance issues where the device becomes unusably slow.
A few of the apps that are taking up CPU:
Many of them are i9's.
Is anyone else having issues like this? These users are on the latest versions of the apps and Big Sur. We've contacted support for Box to see if it's anything on their end but nothing yet.
We use Sophos. For one user Sophos scanning all the files from Box.
We have rebooted multiple times, quit the apps, checked and updated any apps and the OS, reset NVRAM, PRAM, and SMC for some but not all yet. Quitting apps and/or rebooting seems to solve it for a short period but then the CPU usage increases again.
As mentioned by junjishimazaki, it will most likely be a system agent you're running using an older framework or kernel extension causing the issue, effect all apps it interacts with.
If you have security products that haven't at least moved fully to using system extensions or ideally run extension-less, then thats what I would look to isolate in the first step for troubleshooting.
Other kernel extensions to look out for is device drivers like DisplayLink for external docks, which stops a lot of the native hardware acceleration of Big Sur as it emulates via software driver over older USB 2 channels for external displays. We see Cinema 4D renders drop frame rates on i9's to 15-20fps with DELL docks using DisplayLink when compared to using their newer docks using native Thunderbolt 3/USB-C connections which runs tech same renders well over 60fps
My company uses Sophos as well and we also noticed performance issues as well as general internet issues. This was due to Sophos conflicting with Cisco's socket filtering extension. Sophos is aware of this and is working on a fix. You can test out Sophos EAP to see if it resolves your issue.