Latency
Big Sur OS version 11.1
How to deal with keyboard and mouse latency? Keyboard types extra letters, mouse out of control.
MacBook Pro 15″, macOS 11.1
Question marked as
There is probably a software conflict. Test in Safe Mode. Now Safe Mode is slow, but you should get any keyboard or mouse lagging. If the keyboard and mouse work normally in Safe Mode (and they almost certainly do), you will know that some third party software (agent, daemon or login item) does not work correctly in Big Sur.
Please run Etrecheck and post its full report here.