Our deepest fear is not that we are inadequate. Our deepest fear is that we are powerful beyond measure.
...should I just play two sides when I play solo?
This is not possible.
I'll play this way for first run-throughs just so I know how to explain the multiplayer game when I sit down with friends.
If that's your preferred method then the best course of action would be to use the multiplayer rules and play two sides.