I'm using 3.5 but to give an idea of the size I use 112Mb (out of
300Mb total) for Workbench. This setup has many extras, fonts,
viewers, editors, 24 bit backdrops and samples, etc.
68k Workbench does not have VM. Check out VMM on Aminet.
You need to buy a copy of Workbench for each machine you want to run
it on.