There are a lot of cities in the Rust Belt and Midwest like I described, with the regional population around 1-2 million which are far away from being mega cities.
In the few examples I've personally visited, the residential density in the older "upscale" neighborhoods tends to come from duplexes and single family houses on small lots (or larger lots with a comparatively small amount of street frontage). There's some large buildings mixed in along with some very upscale condos and row houses.
Outside of extreme cases, infrastructure costs tend to become dominated by how long the road or pipes are, rather than the number of people using them.
In the few examples I've personally visited, the residential density in the older "upscale" neighborhoods tends to come from duplexes and single family houses on small lots (or larger lots with a comparatively small amount of street frontage). There's some large buildings mixed in along with some very upscale condos and row houses.
Outside of extreme cases, infrastructure costs tend to become dominated by how long the road or pipes are, rather than the number of people using them.