I'll give my input only on what insights we've gleaned while running CodePen. Two things.
Find the minimum amount of process that works to coordinate your team and formalize it. We were pretty ad hoc when we added people to the team and it felt inefficient. We've come up with processes we follow when doing our work and it's helped how we communicate. Everyone understands how we decide what to do and when we do it. Add the fewest number of steps you can. Team happiness is still the most important thing.
There are great ideas and there are great ideas the team can accomplish. We hold back on adding features until we feel we can give them the love they deserve. For example we've wanted an API for a long time, so have our users but we've never had the time to support it. Five years in we can finally start discussing adding an API to CodePen.
One reason to come back often is that featured work (Pens, Posts, Collections, and Projects) are sprinkled out continuously pretty much all day every day.