We're bootstrapping SaaS service as two co-founders for two years already. I would say don't document anything except the code (if you really want to). Don't track anything, don't create any reports of some sorts for the sake of creating.

Only thing you should really care about is how you product solves pain points for the user. Measure user retention and revenue.

As a young enterprise you should only care about how to survive and how to get users. Nothing more, nothing less.