From my understanding, towns create duplicate copies of food collected and can send that food to cities, while the production they collect get turned into gold. Although we have no way of knowing for sure, I would guess that the rate at which towns turn production into gold is not efficient*, so in the end towns are amazing at generating food, probably worse at generating production, neutral? at producing gold, and presumably worse at producing more advanced resources like science and culture due to the lack of urban districts. This seems like a decent trade off where a town heavy empire can grow population faster than a city heavy empire but will lag behind in production, science, and culture.
However, upon hearing about town specialization I do wonder if it will ever be optimal to specialize towns in anything but food. It seems to me that you'd want to turn your high production settlements into cities and keep your high food settlements as towns.
*Based on past iterations of civ turning your production into gold (wealth, city projects) and then back into production (gold rushing) is extremely inefficient.
However, upon hearing about town specialization I do wonder if it will ever be optimal to specialize towns in anything but food. It seems to me that you'd want to turn your high production settlements into cities and keep your high food settlements as towns.
*Based on past iterations of civ turning your production into gold (wealth, city projects) and then back into production (gold rushing) is extremely inefficient.