How to start video record from PC?
scrcpy is a free/open source project which allows you to mirror the Android device and control it from the Windows/MacOS/Linux. It does require the device to be Android 5.0+, and have adb developer debugging enabled.

Once running I was able to with a Pixel 2 and a MacBook Air:


See the Pixel 2 screen on the MacBook Air screen
Scroll on the Pixel 2
Click on the camera app
Switch to video recording in the camera app
Click record
Click stop recording 


without touching the phone.

You would still need to get the video off the phone but the video quality is of the native camera app.