True that, but
a) I kinda suck, can't even beat Monarch yet, and
b) I don't (think I) know the game well enough to spot the advantages such a play style is yielding.
Bonkers!
a. I haven't even tried to beat Monarch (or any particular level for that matter) and that hasn't stopped me from experimenting.
b. You spelled out the advantage of having more but smaller cities in your post. Building cities closer together gives lower maintenance from distance. Go for Wonders with global effects, like Statue of Liberty, and cash in on the number of cities you have.
Some more ideas:
Try to focus less on buildings (as you'd need more of them) and more on units (as you can maintain more of them with more cities). Take advantage of other stuff that affects all of your cities, like certain Civics. Don't go for Representation and Bureaucracy as they only affect one or a few cities. Capitalize on civics like Vassalage (as it gives you additional upkeep-free units for
each city) and Mercantilism (as it gives you a free specialist
per city - but make sure to run it in tandem with Caste System if you don't wanna invest in costly buildings).
Don't bother with Wonders that give happiness bonuses, or to buy luxuries because you probably won't need them. The same with stuff that gives your cities health - chop those forests and don't worry about the jungles or floodplains.
Religion can also be helpful, as it is isn't that costly to spread to all of your cities (compared to building the same set of building in every city). You get both a happiness and a culture benefit, and if you go for certain Wonders (like the Sistine Chapel) and Civics (the religious ones, depending on what your current focus is) you get additional benefits in these cities.
Asoka might be a good choice for a leader, as the Spiritual trait it makes it easier to change Civics and the Organized trait enables you to use the more costly ones. Also the Fast Worker can get all of those tiles your cities need to work up in no time, and allows you to alter improvements with changing needs.
Speaking of which, Slavery can also be effective longer because it will stay cost-effective with smaller cities. Let those closely built cities share food resources in order to grow back faster, by alternating what tiles they work. And once a city is above its happy cap, whip it!
Now I'm doing your work for you, and thats no fun.

Personally I don't think this game is about climbing the difficulty ladder, but rather about this exact kind of experimentation. It will also make you a better and more versatile player.
