I think I am on to something. I am now writing my XeLaTeX document in Latexian which has command suggestion, syntax highlighting, tabs and parses the LaTeX/XeLaTeX document and gives you an outline which you can use to navigate your document. It also has a live preview, but I don’t use it since Latexian does not do biber (pun not intended).
For typesetting, I instead use TeXShop which I have configured to use an external editor, so the editor does not pop up. I just get the console and the PDF output windows.
Also, since I am using XeLaTeX and biber, UTF-8 is no problem at all!