Here are some questions you need to be able to answer. (Mostly since this is a rehab).
(Assuming that you will mostly try to use z-wave for switches and dimmers, etc. It generally works well…)
The foremost question is the state of the existing electrical wiring the the house. Every z-wave switch that I have encountered requires 3 wires – line,load, and a true neutral. N-way switches require 4 wires – line,load,neutral and a fourth “traveler” on the main switch in the N-way. Auxiliaries in the N-way are slaves and use one wire to communicate state changes to the “main” which actually controls the circuit.
N-ways are a problem because there are multiple legal ways to wire an N-way from an electrician’s perspective but not all of those will work with z-wave switches because of the specific wiring.
In my personal house I have two N-way circuits - one for the entryway stairs (I live on 2nd and 3rd floors of a condo building) and a second for the stairs from floors 2-3. The construction electricians wired the entryway stair circuit in a way so that it could be automated, but the stairs from 2-3 are not compatible because of the specific wiring. Every N-way circuit needs to be specifically documented wire-by-wire to determine what your options are.