You can launch xfce4-terminal with customised icon, title, geometry and so on. For example,
xfce4-terminal --icon=/home/user/scripts/green.png --title="Custom title" --geometry=100x30+130+200
The above command would open a terminal window with specified icon and title, 100x30 characters in size, positioned 130 pixels from screen left and 200 pixels from screen top.
You could then create a bunch of scripted aliases for such commands, e.g. rterm, gterm, bterm, for variants with red, green, and blue icons, and so on.
I find colours better than any other way of distinguishing things.
Getting your terminals onto the desired workspace can be achieved with wmctrl -s. When scripting these, I'd add e.g. a 50ms pause to allow the window to reliably appear, and then issue the wmctrl instruction to push the session to whichever workspace you need. Perhaps have variants like rterm1, rterm2, gterm1, and so on.