I've been tinkering around with my Openbox desktop. I've got a pretty nice setup for now, but I would like an "embedded" rxvt-unicode. I know this is possible, according to this guide (I've followed it before, successfully): http://bleedux.wordpress.com/tag/rxvt/

But more specifically, and especially as the ~/.Xresources file sets parameters on a global basis for all rxvt-unicode terminals that I call up, I would like to still be able to call up additional, "normal" terminals with borders, a scrollbar and the like. Is this possible or am I just asking for too much?

Another option that I like less would be to install the non-unicode rxvt and use this one for my desktop while my hacked-the-hell-out rxvt-unicode would remain as my regular terminal.

All X client applications take commandline arguments to define their appearance and other attributes. You could create an alias that defines a particular collection of commandline arguments for your application. I don't user rxvt, but I understand it is a terminal of some type; I use xterm.
Then just use the newly defined commmand name to launch the application with the given arguments.

--- rod.