I've read a fair bit about how the founders of the Qing dynasty essentially created Manchu as an ethnic identity and how they and many of their successors used it to enforce class hierarchies and as a cultural and political tool. However, I haven't read much about how Manchus and the Manchu identity were affected/viewed/treated after the Qing dynasty gave way to the Republic of China. Were Manchus still treated preferentially? Did the emphasis on Manchu vs. Han still exist by the time the Qing dynasty collapsed?
I can tell you've read Mark Elliot's book. I don't have an answer, because no one really does. Mark Elliot is currently working on his latest book, which will address exactly the question your posing: what was the experience of the Manchus as an ethnic group in the 20th century?