This blog entry from You Suck at Racing has a commentary by the author during a race:
https://yousuckatracing.wordpress.com/2016/09/25/video-thunderhill-west/
The first half is the driving line, but the second half discusses racecraft, passing, etc as voiceover narration to the race. Pretty interesting.
Here is a direct link to the video:
https://m.youtube.com/watch?v=sCEV8KkFdxc