Does emacspeak have graphical interface like menus to access functions, or is it fully command-line controlled?
Neither. It's all controlled inside of Emacs itself.
Are you specifically looking for a menu of emacspeak functions, or a menu of emacs functions? If you're looking for Emacs, you can hit f10 to get a menu bar type thing, which Emacspeak will read.
If I use espeak, does the voice change feature work? I do not know exactly how it works because I've only heard of it, so I can not explain it very well.