If I have an object with a bunch of empty gameobjects with just Transform components as its children, but nothing attached to those- and the parent object is moving and rotating, is the engine keeping track of the position and rotation of each one of those points every frame, or are they only being recalculated relative to the parent when a script addresses one of them and ignored the rest of the time?
World positions of child transforms are updated on demand, so if you’re not accessing them and there are no Renderers/Physics/And other stuff on it then world matrices shouldn’t be calculated.
On the other hand if you have lots and lots of them they might consume some performance, because Unity has to allocate memory for them and do some basic managment.