I think we have the same amount and kinds of "stuff" open, but where we differ is I place things on virtual desktops (organized by a tiling window manager), of which I have between 4 and 8 at any given time. (Typically: web, coding, VMs, one or more bug logs, one or more back-burner projects.)

I can't think of a situation where I'd need to focus on all the things you list simultaneously – even just having e-mail on the screen while I'm trying to code is distracting – so I'd rather have them hidden. Sure, I'll have a couple code windows and documentation or logs open, but that fits with room to spare on a single monitor.