Placing Oval Slot Shaped Hole VS Drawing slot lines in Edge.Cuts layer

In KiCad 8, let's say I draw a square outline on the Edge.Cuts layer to define the shape of my PCB.

If I want to create an internal cutout within this square (a slot that will be milled out), I draw it on the Edge.Cuts layer. This slot will be milled, making it a void in the PCB.

Alternatively, I can create an "oval slot hole" by placing a pad in the PCB Editor. To do this, I set the pad properties to NPTH (Non-Plated Through Hole), Mechanical type, and choose an oval pad shape.

If the dimensions and the locations on the PCB are the same as my line drawn slot, the 3D view will show them as identical.

1. However, for the machine that processes the PCB, is there any difference between these two methods?

2. A closed cut line on the Edge.Cuts layer must not overlap, as it will cause the shape to be invalid (resulting in two holes disappearing on the PCB/ see the image). In contrast, overlapping two pad's oval holes doesn't seem to affect the shape. Is there any problem with using the latter method to instruct the machine to mill slots like this?