Already got the new house wired up with cat 6a going everywhere (cat 7 was just too costly to look at)

4 to the TV (1 for internet, 3 for hdmi over cat 6a)

Each bedroom having 1-2 ports (4 for the computer room)

So adding a few wifi access points or a Mesh Wi-Fi looks like the better way. (Thanks for the advice) 

The sonos sound system is already using its own Mesh Wi-Fi and so to the Z-Wave relays on the lights and curtains.

Anyone know if these would cause issues with Ubiquiti AmpliFi Mesh Wi-Fi?

I am guessing not

Z-wave uses 921.42MHz (New Zealand)

I think sonos still using the 2.4 GHz band for its own Mesh