Let's agree on this: you can critique me as much as you want. If I feel like I disagree with you on something, I will let you know with no offense taken.
As for your lips study, I think you're definitely thinking in the right direction. Expressions and volumes read very well. The rendered ones look very believable. At this point I would only recommend looking closer at how the corners of the mouth work. Most lips don't exactly overlap. It's better to use lips without lipstick for reference at first.