Is it possible to Mix Multi-site and Stand Alone Installs on the Same Domain?

Is it possible to setup the Multi-site WordPress to

(a) do some blogs through multi-plugin installs and

(b) to do other blogs as individual installations separate and appart from Multi-site?

Specifically if I were using the Multi-user option, could I implement one of the following subdomain sites as a separate install and the other two as a multi-user install?

Does it make a difference if I am doing this with sub-domains as opposed to sub-directories?