Ok, after reading ts2995's post and thinking he at least found the root cause, he did, I did a bunch of testing and figured out how to capture some lag free webcam video.
1. Plug in your webcam
2. Open VLC
3. Click Media > Convert/Save
4. Select the "Capture Device" tab
5. Select your webcam in the "Video Device Name" drop down box
6. Select your mic in the "Audio Device Name" drop down box (I haven't worked out the audio yet because I am choosing 'none' as I don't need audio for what I'm doing.)
7. Click the "Advanced Options" button and tick the "Device properties" box. (this is what will make those windows popup that ts2995 was reffering to)
8. Click the "ok" button
9. Click the "Convert/Save" button
10. Tic the "Display the Output" box if you need to see what your recording live, to aim the camera I assume. If the camera is all setup and you don't need to see the picture live, you don't need to do this.
11. Select the "Video - H.264 + MP3 (MP4)" profile then click on the little wrench button next to it.
12. Select the "Video Codec" tab and tic the box "Keep original video track" then click the "Save" button
13. Click the "Browse" button and choose a folder and filename for the video
14. Click the "Start" button and the "Properties" box will popup. Click the "OK" button on this first one (This is what ts2995 was reffering to)
15. A second properties box will popup. In the "Color Space/Compression" drop down box change it to "MJPG"
16: I also changed the "Output Size" to the default. (1920x1080 for me, this is the cameras default)
17. Click the "Apply" button
18. Click the "OK" button and the recording will start.
There's still a little delay between waving your hand in front of the camera and seeing it on the screen but it doesn't affect the recording.
I'm doing all this on a 10 year old HP Envy laptop running Windows 10 with a no name 1080p wide angle
Webcam I got off Amazon.
I tried using the built in Camera app but it stops recording after 3 hours because M.$ thinks everyone is forking stupid and they must control everything we do. If you need a video shorter then that, the Camera app would work fine for you.
We are trying to identify exactly what is leaving tiny excrements on our back patio at night so I need to record for 10 hours at a time.