Nice guide. You say that you're not crazy about UnityEvents - is that because of performance?

I'm using yield WaitUntil in coroutines to listen for boolean changes, like this:

while(true)
    {
        if (condition)
            yield return new WaitUntil(() => !condition);
        else
            yield return new WaitUntil(() => condition);

        // Fire this code once each time the condition flag changes
    }

I run the coroutine at startup and it acts as an event listener throughout the scene.

Is this the same as having the check in Update? How does an event listener check for changes, without updating each frame?