I'm actually quite fond of the new compose window and I fall into essentially the same category of email user as you. My anxiety was in fact lessened a bit by the chat-like (and therefore more casual) vibe, thanks to large expanses of white space making me feel like I /must/ fill them with text. Email anxiety is no fun, maybe a native client would be the best way to ensure your workflow is optimized?
I am checking out Airmail thanks to an older HN thread. Cheers!