Construct's memory management relies on identifying which instances are placed in layouts. So it's better to place all instances that may be used on the layout, and destroy them in 'On start of layout' if they're not needed immediately. Then Construct will pre-load all the images for them when starting the layout. If you don't place anything in the layout and only create them in events, it can jank the game as it has to load images on-the-fly.