useEffect and useLayoutEffect are called in the order they appear in your code for like types just like useState calls.

Does useEffect always run on first render?

By default, useEffect will run on initial render as well as every future render (update) of your component.

Which useEffect runs first parent or child?

Right now, the effects in useEffect fire children-first. I know this makes sense, since the behaviour of the first render has a close correlation to cDm.