It's simple, at least in Chrome.
Control-Click on the Compose button. Your Compose opens in a tab - with To and Subject line exposed, full view. Alternatively, shift-click to get a new window.
Shift-C works too, opens a proper compose. Ctrl-C doesn't work though.
Reply isn't as elegant. Shift-R when in the context of a menu creates a right sided 'pop-out', shift-click or ctrl-click on top right icon to get it in a separate window. Alas, subject line is still hidden, that's another click to expose (Google hates subject lines, no kb shortcut either). Also, prior text is hidden -- yet another click.
Shift-A replies all in new window.
Have I mentioned I don't like Google?
We need a Chrome Extension that fixes Reply.