I think I'd imagine a sort-of futurized ancient-greek aesthetic; the aesthetic architectural stylings of ancient greece combined with tinkertech materials, efficient urban planning, accessible & free public services (libraries, schools, housing, food+water distribution, etc.), vertical expansion (big, tall buildings with elevators and staircases and the like as opposed to urban sprawl; very efficient use of the full space available in the city). Probably also a lot of Vegetation, public spaces(parks, playgrounds, ) in a way that borders on the Solarpunk aesthetic. Little career-criminal or gang presence, if any (there is literally no need to get sucked into the dangerous criminal lifestyle when your basic needs for food, water, shelter are already met). So we essentially end up with this futuristic city dressed up in the clothes of an ancient city. Maybe there are giant divine-blessing-amplifier shrines throughout the city, serving dual-purposes as tourist attractions and power-boosters for Joe. Also probably full of some of that bastion-tech that makes everything in the area self-repair and work better and etc.
There's Also the option where he refuses to limit himself to one aesthetic style, and ends up having every district of the city conform to a Different aesthetic. Solar punk in one area, futuristic sci-fi in another district, greco-roman architecture in yet another district, etc. Potentially even Color-coding the different types of locations; green for hangout spots, blue for public services/government, red for businesses, yellow for transit, etc. allowing people to figure out how to get where they're going just by following the colors.
I imagine that the practical elements of verticality, urban planning, etc. would remain in the second option, though. maybe with use of certain technologies favored in different locations in order to make normally un-practical design decisions practical.
tl;dr: i vote scifi greek classical with a mix of Solarpunk thrown in OR a mix of varying architectural styles and aesthetics in different areas/districts of the city.