My rule of thumb is to have 3 ideas before I call something a song, but if one of the ideas is weak, I may eliminate it and still have 2 ideas.

Instead of trying to come up with variations on a looping idea, I'll contrast 3 different loops. It's okay if it sounds like you're switching from one song to another. Try to avoid repeating anything more than once. The third repeat legitimized, but it also causes the idea to disappear in the listener's mind.

Just make tracks?

Isn't this the easiest way?

The only difference I know between programming a mono or a poly is that you have more modes available besides legato and portamento, so you can play more than one note at a time.