A Behavior is associated with a specific View- the callbacks refer to this View as the “child.” Many callbacks also pass a “target” or a “dependency,” which is the View that triggered the callback.
Types are a Good Idea. Computers are relentless at finding errors, humans not so much. You can get away without using types, but large projects and teams will run better with them.
If you are trying to decide between a few people to fill a position, always hire the better writer. It doesn’t matter if that person is a designer, programmer, marketer, salesperson, or whatever, the writing skills will pay off.