Recent developments in modular construction, especially recent factory-pre-assembled room modules now being employed in hotel construction suggest you may in the future see a lot of double-walls between units, some light-gauge steel studs between heavy-gauge steel structural members, all supporting interior sheetrock (or equivalent) with blown cellulose or glass-fibre insulation or sheets of rigid polyisocyanurate insulation, all with cold and cold water piping, waste water piping, power and data in flex conduit with connectors at each wall intersection.
Think steel lego assemblies which stack and align.
To see what I mean, look up on You Tube the B1M channel and look for the video on the new Modular Marriot which is going up as we speak:
B1M YT vblog article modular hotel
It's also worth recognising that one implication of this kind of architecture is that as it becomes more common, the reuse of shipping container approach which has failed to gain traction will become far more attractive - and so you might well see mid and high rise residential structures where the main structural components are super-heavy gauge steel (in scale with what you see in a bridge or super-high tower) and those create an accepting framework which accepts the shipping-container-sized modules and locks them in place. These larger frames need not be rectilinearly-aligned beyond the scope of the individual modules, depending upon the nearby structures and space envelope constraints - so you might see some very strange twisting leaning overall building envelopes, as long as all the forces balance and the overall structure can withstand rain, wind-loading (a huge deal in high-rise constructions) and whatever seismic forces can be expected on that specific site (so if on the ring of fire expect huge triangulated trusses, both horizontal axis and vertical) so your characters will need to be able to navigate between the larger steel members, possibly knock out light-gauge steel studs, cut through polyiso rigid sheet insulation or tear through blown insulation and avoid power conduits and PEX or BPEX flexible water piping; if the building was lower-cost and did reuse shipping containers, there might still be medium-gauge steel sheeting at the centrelines of the double walls between units too.
Hope that helps.