You can use any combination of clones as long as you have 3 pitchers and 4 position players to fill out your roster.
As an example I used the same player to cover all 3 outfield positions and my DH as well as 1B, then I selected a Catcher, a 3rd baseman and 1 player to play SS and 2B
After that I filled out my backup positions with the same 4 players.
Let me know if that clears up your questions.