Urban settings must deal with the issue of how to stat civilian NPCs.
In my view, D&D ‘classes’ by definition mean ‘combat training’. Some people fight with magic, some people fight with swords, some fight with stealth, and so on. In this way, ‘noncombatants’ have little or no class levels. Normally NPCs have no stats. Simply assign whatever stats seem to make sense, if and when appropriate. A powerful and experienced noble, may well be only Fighter 2, for example, depending on actual combat experience. A sage may be able to cast a high level spell, but be only Wizard 3, in terms of combat experience. And so on.
In these cases, it is extremely useful to use the 5e tier system.
Novice = Level 0
Student = Levels 1-4
Professional = Levels 5-10
Master = Levels 11-16
Legend = Levels 17-20
Epic = Level 21
These levels specifically refer to the combat classes. But use the general expectations of power and competence, to ballpark the tiers of noncombat experience. For example, is the chef at a restaurant more a ‘Student chef’, a reliable ‘Professional chef’, or perhaps a celebrated ‘Master chef’?
As a rule of thumb, a population of a million, being a small nation or a big city, will produce a handful of individuals operating in the Master tier. For example, the medieval small nation of England, can produce a Beowulf, who is arguably about Fighter 12 or so.
A Student is familiar to peers. A Professional is familiar to a community. A Master is familiar to a nation. A Legend is familiar to the world.
All of the above depends on the tone of the campaign setting. But it is a useful default assumption.