Athens polikatoikias — concrete apartments with tiered balconies — were built quickly to create affordable housing, but their design has stood the test of time.
The Fully Automated rulebook has some cool ideas on housing. I think this article has nice examples and discussions around features of successful apartment buildings/neighborhoods, including the vertical rather than horizontal stratification, which might be worth considering in solarpunk worldbuilding.
I like this style. I live in an apartment that isn't quite this, but isn't radically different either.
There are two apartments in the building which have balconies that are enormous: the apartment unit is about 1000 square feet, and about 300 of that is the balcony, and I think it's brilliant. I'd love to see more apartments in which the outdoor space makes up a large fraction of the total space.