You can't go by population size alone.

The city I'm in now (Traverse City) has a population of only 14,000, with a metro area about 10 times that size. But it's the only city in northwestern Michigan, so it has a good hospital and library, museums, bookstores and coffee shops that you'd expect in a larger city. It's also a resort city, so it has a lot of good restaurants and recreational facilities. The central area is very bike/walk friendly, but the Sprawl Zone is pretty bad. The closest big city is Grand Rapids, about 135 miles to the south. Over all I would give it a "B" for carfree living.

Most small cities/towns have more amenities than they used to. I briefly lived in Charlotte, MI (pop. 8,000). There were the major big box stores so you could buy most things you really need. However, I found few of the "finer things" like restaurants, libraries, bookstores, coffee shops. A trip to the ER seemed like a suicide run if you had a serious health problem. For recreation, road biking and mountain biking were about all. The big city was 22 miles away. Bus service was very bad--no fixed routes, just unreliable and slow on-demand vans. A trip to the city was an all day affair, whether you went by bike or bus. This would have been an acceptable carfree location only if you were satisfied with the amenities in the town itself. I would give it a "C-" on the carfree scale.