For a distant skyline, a big aperture change often won’t create a dramatic visible difference because most of the scene is far away, so depth of field is already very large. That means both shots can look similarly in focus.

What does change is lens performance:

• At the widest aperture, lenses are often softer and may show more aberrations.
• At very small apertures like f/25, diffraction reduces sharpness.
• Many lenses are sharpest a few stops down from wide open, often around f/8.

So the difference may be subtle, but it’s there in image quality rather than obvious background blur.

Manual mode is not required if auto gives you good results. Manual mainly gives full control over exposure choices. For cityscapes/landscapes, aperture priority is often the most useful mode: you choose the aperture, and the camera sets shutter speed. A moderate aperture such as f/8 to f/11 is commonly a good choice for sharpness and depth of field. Very wide apertures matter more when you have nearby subjects and want shallow depth of field.