These are snapping candidates and not paths.
I suggest to watch this tutorial: https://vimeo.com/188104194
The short answer is to turn off "Show snapping candidates" to hide the pink lines under snapping option.
For Affinity designer, production version. On the FX for a layer, the "Fill knocks out shadow" isn't working. If you click on the option, a tick appears for a millisecond and then disappears.