Awesome job on these last two. Your value control is getting better and better. Great job on the sharpness you achieved in the foreground of #10. If you put a sharpen filter over #9 and #10 I think it would make them even closer.
I think keeping zoomed out for these studies is probably your best bet. What I personally found helpful in my later studies was to lay in everything with those textured brushes, then to achieve sharpness, I went over certain forms and edges with a hard round- size jitter on, but with full opacity and flow. At first it scared me, because it was out of my comfort zone and it looked terrible up close. If I kept it zoomed out, it looked pretty good. It sped up my process a lot, I learned more about choosing the appropriate values, and I think it's appropriate for this type of study. I also used the sharpen tool or sharpen filters sometimes. Just something to think about.I'm a bit unsure as to how much to zoom in when doing the details, without losing trace of the ref. So mostly, I keep it zoomed out and work on it as it is. Will have to figure out another way to approach these studies.
Honestly, all in all, these are really great.