Hey i noticed you were curious about smoke when it comes to how to draw it. Smoke wrapping around objects is a pretty interesting study. I tried doing it myself and my smoke looked just like yours does in your black figure picture.
Here is my attempt
Well you see, i took a photo of a match being lit on fire with a torch. It resembled the exact behavior you were trying to create so i thought it would be a perfect study. Now the medium i used is much different from yours as i used chalk pastels, while you on hand are using digital media. Well what ilearned was, i tried to do everything i could to give the gasous form shape, but nothing really worked. The gas was so thin, it was see through light goes through it. I didn't understand how to draw this or capture what i was trying to capture. When i added color on top of the match, it overwhelmed the match. But, if i added light color around the flame, it made the flame too bold. No matter what i did the flame remained flat and didn't gain any form.
Well.... I had a time constraint my friends album was coming out and i wanted to get his project done, so i skipped all the practices and just jumped right into this project.
If you look i used the same flame techniques i learned from my study into that piece. Now that piece really isn't that impressive either, but hey it was the best i could produce given the conditions.
Basically what i learned is, smoke and wrapping smoke around objects revolves mostly around linework and not lighting and shadows. Yes lighting and shadows are still important, but if your linework isn't strong enough you will lose the form of your smoke and you will get nothing but flatness as a result.
Now i could be wrong aswell.
Also another tip you should consider, try not to draw things that come from your imagination when you are learning. You can.. But try drawing things that actually exist too. The reason is because people need things to relate to your artwork, real-life things. It makes your work less confusion and easier on the eyes. All because you model after real-life doesn't mean it has to be real-life. You just need to capture simularities and modify them enough so it still maintains a familair form with something but it can indeed be completely abstract aswell.