MY recommendations, others will disagree.
You can never have too much Ethernet in the walls. CAT5E is sufficient for most homes as it is rated for 1 gigabit per second. Unless you are getting 10Gbit from your ISP, you don’t need CAT6. CAT6 is rated to 10Gb per second, but other than businesses, I have never heard of anyone with 10Gb speeds from their ISP. If someone tells you that you need CAT7, then either they don’t know what they are talking about or they want you to pay them for expensive cabling.
What is Cat7 - And Why You Don’t Need It
If I were building new, I would run CAT5E or CAT6 from a central location, call it a server closet, to every room in the house. Have the electrician just drop the Ethernet cable into the wall with a 3-ft tail. Roll it up and tape- NOT STAPLES- it to the stud. (For the electrician: This is low-voltage data cable and no code I am aware of requires staples like line-voltage cables). Then drywall over it. Make a map of where the drops are located so that when you decide that you need Ethernet in this room, you can cut a hole for the wall plate. I am in the US and this is what I use.
Don’t forget the ceilings. You may want to install WiFi access points in the future.
Most important tip about cables: LABEL them.
Which wire goes to which room?
Topology:
Do NOT buy a hub. Home Assistant can act as the hub for Z-Wave or Zigbee with just a USB dongle. (A Zigbee dongle is technically a “Coordinator”).
[Tip: plug the dongles into a USB2 port. USB3 (because of its data speed) can generate harmonics that will decrease the range of 2.4GHz devices. Especially Zigbee].
It doesn’t really matter which topology you start with, Ethernet, WiFi, Xbee, Z-wave, USB, because you will eventually have devices on all of them. No one topology can provide devices for all IOT things. My personal recommendation would be Ethernet and Zigbee. Ethernet because you will find more devices with Ethernet than most others. And WiFi devices tend to be the cheapest. Zigbee because, in my experience, connecting Zigbee devices to Home Assistant is pretty easy.
Lights:
Unless you really NEED color, do NOT buy “smart LEDs”. They are expensive and you can use dumb (cheaper) LED lights and smart switches. I prefer in-wall switches like this:
Switch modules like Shelly or Sonoff are best for using existing switches but using a switch that has WiFi or Z-wave already built-in eliminates some wiring and doesn’t crowd your fixture box.
Summary:
Don’t sweat the details.
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