Using Windows 10 x64 1809 17763.292
Mouse with 1000hz response rate.
Posting this because it can be usable info.
After Recording video with ReLive if you grab window and try to move it with running task manager you will see massive cpu consumption by process dwm.exe. If you kill this process it will restart instantly and there is no mouse lag after.
To repeat bug you need to record video another time with ReLive.
Using HEVC encoder with ReLive.
Tested HEVC VCE with Handbrake - no mouse lag after, so problem not with encoding engine.
If need to check what response rate of your mouse you can use this: