Running two separate instances of Safari in the same user session
Solution 1:
You can also type in the Terminal.app
open -n -a Safari
This will open an new instance of Safari even if one is already running. Not every application supports this, like Finder or FireFox. Those applications prefers to have one instance running at a time.
Solution 2:
Safari does not support multiple profiles, so you will have to keep using multiple user account.
If all you want is a separate browsing environment with different accounts (cookies) used, you can try using Private Browsing
