The flour should not be packed? I've always done it like that, it seemed so obvious that that would give a less random result that having it loose. I guess I'll weigh it and check against the markings on my measuring cup next time.

Brown sugar should be packed; flour must not be — you’ll get substantially more mass per volume than the recipes assume.

Some pack, some sift and scoop. You have to know what the recipe wants. Weigh is in my opinion superior, it just wasn’t widely accessible before cheap digital scales.

Weighing is the only weigh.

four is alway sifted - to get the mouse droppings out. In our modern world nobody has mouse droppings in flour but tradition is still strong. Weighing doesn't care but if you are scouping as much air as possible is what the recipe assumes.