Sometime ago (about two and a half years) I had developed a method for Drop Caps for "all e-readers" (epub and mobi). With that method, no matter the font-size or the font family choosen by the reader, the Drop Cap would be consistent. Since I don't have all kind of ereaders, I had tested the respective epub with ADE (2, 3 & 4), Kindle Previewer (2.9x), Kindle for Android and my own Kindle device with very good results. All of you can check the respective epub below (attached to this post).
Recently, because of my issue with Drop Caps (Drop Caps with a symbol before) with the new Amazon format (.kfx) I went back to test that method with Kindle Previewer 3.2x. Again, the results were good, BUT KP3 -with that method- didn't generate "enhanced typesetting". And I wanted enhanced typesetting
After a lot of trial and error, very recently I could develop a new method, again based in .svg images, that WORKS with kfx and enhanced typesetting. I don't know if my experiments are representative, but IMHO and FWIW, it's not possible to have consistent results by working only with .css properties to handle Drop Caps. The only way I found was to use images, and for this case, svg images.