I would use a flat surface similar to the sun room with applied low profile trim to echo the detail on the new garage door. Paint it the same white as the garage. You'll hardly notice you reduced the side of the garage door. The new door should be the same style with a 3/4 window.

I would reseal the entire driveway or replace it.

Thank you for the suggestion. I agree we do need to replace the full driveway too.

I've seen people do cobblestone at the edge of a brick wall--wish I could find a photo to show what I mean. You could also carry the stone veneer over to the porch.

I would get a carpenter to to make something similar to sidelights on a front door set, i.e., a panel of windows. If you don't want anyone seeing in, they could be lined with sheers. It would also have the benefit of allowing light into the garage.

For street appeal, trim the hedge in front of the sun porch level on top, a few inches below the windows. Trim them as if one long bush, with rounded shoulders and front. Dome shape, not ball shape, meaning don't undercut them at the bottom.