In the limit, you build roads too small for cars, like in the old walled medieval cities in europe. They are in general great places to walk and terrible places to drive.

In the other limit, you build like e.g. Detroit suburbs, where it's essentially impossible to do anything on foot, ever.

If you have to choose which one to be more like, curvy narrow roads are the way to go if you care about pedestrians.

Add to this the fact that, if you provide space for cars, they will take it up: adding lanes / width / parking increases car usage to a greater extent than the space added, such that you end up drawing more congestion to the area than before it was improved.